Homebrew Feat: “Whirlwind Sentinel” –critiques and suggestions please

The DM and I have worked it out, so it’s a bit moot, but I’d still like the community’s opinion on whether or not this homebrew feat is balanced for D&D 5e.
Inspiration taken from:
Sentinel (PHB 169)
Slasher (TCE 81)
(Sorry, feats not in the SRD)

This is for my lvl4 halfling barbarian; he has a STR of 17, so I really really want that sweet +4 mod, but taking the attr bonus is ‘boring’ to me. The purpose of this feat is to give him some more battlefield control (a la Sentinel; plus he took the Wolf Totem option at lvl 3), while also limiting the instances he can ‘do the thing’ (a la ‘Slasher’ feat)
Here’s what we came up with:

  • Increase your Strength or Dexterity by 1, to a maximum of 20

When using ONLY a melee slashing weapon* (with or without a shield):

  • When you use your Reaction to hit a creature with an Opportunity attack: if you don’t have disadvantage, roll a second d20– if the second d20 would also hit, reduce the creature’s speed to 0 for the rest of the turn.
  • If a creature you attacked on your most recent turn makes an attack against a target other than you, you may use your Reaction to make an attack against that creature

*we wanted to underline that this feat only works with slashing weapons, but not prevent a flaming axe or shields

Do the Hunter ranger’s Extra Attack, Whirlwind Attack, and/or Horde Breaker features work together?

At level 5, all rangers get the Extra Attack feature:

Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.

At level 3, the Hunter ranger archetype gets Hunter’s Prey, which lets them choose from 3 possible features. One option is Horde Breaker:

Once on each of your turns when you make a weapon attack, you can make another attack with the same weapon against a different creature that is within 5 feet of the original target and within range of your weapon.

At level 11, Hunters gain the Multiattack feature, which lets them choose between the Whirlwind Attack and Volley options. Whirlwind Attack says:

You can use your action to make a melee attack against any number of creatures within 5 feet of you, with a separate attack roll for each target.

Am I right that Whirlwind Attack can not be used with Extra Attack, because you do not use the Attack action to make a Whirlwind Attack? Generally, can Extra Attack be used with any of the Hunter ranger’s special attacks?

I think with Horde Breaker, the “different creature” clause excludes any creature originally targeted with Whirlwind Attack. This means unless you have a reach weapon, Horde Breaker is useless with Whirlwind Attack. Am I mistaken?

How does Whirlwind Attack interact with Travel Devotion or other swift action movement?

Since swift actions can be used during other actions, what happens if one uses a swift action movement (for example under the effect of Travel Devotion) in the middle of a Whirlwind Attack?

Would the character
A) continue making attacks while moving?
B) Interrupt the attacks with a move?

In either case, would any “new” enemy – not present when beginning the attack but coming in range due to the character’s movement – be a valid target for continuing the Whirlwind Attack?

(Note I’m asking for explicitly movement as a swift action, not a move action gained through a swift action)

How does the Ranger Whirlwind Attack feature compare to the Volley feature?

The goal of this question is to compare both Ranger level 11 features Whirlwind Attack & Volley and examine their comparative strengths and weaknesses for Rangers.

Whirlwind Attack

You can use your action to make a melee attack against any number of creatures within 5 feet of you, with a separate attack roll for each target.

Volley

You can use your action to make a ranged attack against any number of creatures within 10 feet of a point you can see within your weapon’s range. You must have ammunition for each target, as normal, and you make a separate attack roll for each target.

At level 11 you would have two attacks available during a normal action so you would need to have at least three enemies within 5 feet of you to make Whirlwind Attack viable from a pure damage output standpoint. The way I see it, you need to have good positioning, a number of enemies clustered, and be willing to sacrifice the utility of focused fire. I have trouble seeing this as being more useful than Volley.

Is there something that makes this choice mechanically competitive besides being in a campaign where you are frequently engaging hoards of swarming melee combatants?

As a rough surface calculation I am looking at volley as ranged AoE which can effectively hit 16 squares, while Whirlwind is a melee attack that can hit 8. The only direct advantage’s to melee attacks that a melee focused ranger could have is a +2 to damage with every attack, or an additional melee attack as a bonus action. So if Whirlwind attacks and hits all 8 squares it can do 16 extra damage on a melee focused build. Or if we went with two weapon fighting one extra attack that would probably max out at slightly less than 16.

At a bare minimum if I could add one single target with volley to an ideal whirlwind I would getting almost the same exact damage spread.

If I were already surrounded by 8 opponents obviously WW is better, but chances are I don’t actually want that to happen in the first place.

Would a slow effect block a hunter ranger from using volley or whirlwind attack?

The Slow spell includes this rule for any creature affected by it:

Regardless of the creature’s Abilities or Magic Items, it can’t make more than one melee or ranged Attack during its turn.

A Ranger who is followed the hunter archetype gets access to volley and whirlwind attack at level 7:

Volley:

You can use your action to make a ranged Attack against any number of creatures within 10 feet of a point you can see within your weapon’s range. You must have Ammunition for each target, as normal, and you make a separate Attack roll for each target.

Whirlwind Attack:

You can use your action to make a melee Attack against any number of creatures within 5 feet of you, with a separate Attack roll for each target.

As I understand it, both of these abilities are considered to be a single attack, albeit with multiple attack rolls. Does that mean the slow spell would not prevent a ranger from using either ability if they were under it’s influence?

Can a Hunter Ranger under the effects of the Shapechange spell use Whirlwind Attack with a Monster’s attack?

The Hunter Ranger’s Whirlwind Attack feature states:

You can use your action to make a melee attack against any number of creatures within 5 feet of you, with a separate attack roll for each target.

I’m wondering whether you could use the shapechange spell in conjunction with this feature, the spell states:

[…] You retain the benefit of any features from your class, race, or other source and can use them, provided that your new form is physically capable of doing so […]

Does this mean that a Ranger who is transformed into, say, a Bulette could use their Bite attack with Whirlwind Attack?

Can you grapple/shove with the Hunter Ranger’s Whirlwind Attack?

The Hunter Ranger’s Whirlwind Attack feature states:

You can use your action to make a melee attack against any number of creatures within 5 feet of you, with a separate attack roll for each target.

The rules on “Grappling” state (the rules in shoving are effectively identical):

When you want to grab a creature or wrestle with it, you can use the Attack action to make a special melee attack, a grapple. If you’re able to make multiple attacks with the Attack action, this attack replaces one of them.

I couldn’t find any other features spells or abilities that allow a creature to make a flat “melee attack”. If they had said “melee weapon attack” instead this would have meant the same thing but specifically have excluded grapple/shove as an option.

I am unsure whether the rules on grappling/shoving mean that the only time you can grapple/shove are when you take the Attack action, which you are not doing when using the Whirlwind Attack feature.

I would like answers to assume that the following ruling made in the Sage Advice Compendium is correct:

Whirlwind Attack is unusual, in that it’s a single attack with multiple attack rolls…

Can you use a melee spell attack with the Hunter Ranger’s Whirlwind Attack?

The Hunter Ranger’s Whirlwind Attack feature states:

You can use your action to make a melee attack against any number of creatures within 5 feet of you, with a separate attack roll for each target.

It does not specify that the attack needs to me a melee weapon attack but only that it must be a melee attack. Does this mean that you would be able to cast a spell such as inflict wounds or shocking grasp if you multi-classed into a class with this spell?

I would like answers to assume that the following ruling made in the Sage Advice Compendium is correct:

Whirlwind Attack is unusual, in that it’s a single attack with multiple attack rolls…

Character Optimization: Shillelagh Whirlwind

I’d like to optimize my character concept:

I want my main damage source to be a Shillelagh’d weapon and squeeze that source for all it’s worth.

Table character limitations:

  • Character is level 5
  • Point buy for level 1 ability scores
  • No multiclassing allowed
  • Variant Humans and Duergar are banned
  • Each character gets a free feat at level 1, provided they qualify for that feat at level 1
  • All official sources are allowed and can be mixed, but UA is only allowed on a per case basis (so preferably not used), no homebrew

Optimization Goals:

  • Highest average damage per round possible, using Shillelagh
  • Secondary goal is highest effective number of hit points, assuming a well mixed pool of damage sources

Bonus points for:

  • Not using UA
  • Actually having a use for my Wisdom score besides whacking with Shillelagh

So far I have:

  • Hill dwarf for the juicy Con and Wis + free HP
  • Go Fighter, archetype Champion for extra attack DPR and heavy armor + shield + armored fighting style
  • Take Magic Initiate feat level 1 for Shillelagh + absorb elements
  • Pump Wis with ASI