Is dispelling nearly impossible to succeed?

The rules for dispelling say:

A Dispelling test is the dispeller’s Counterspelling + Magic [Astral] v. spell’s Force + caster’s Magic (+ amount of Karma spent on quickening the spell, if any) […] Every net hit reduces the number of hits the caster had in casting the spell.

Our mage cast a Force 10 illusion with 8 magic (6 + 2-Force focus). She had 8 hits in her spellcasting test. An enemy mage would like to dispel that illusion.

If I understood the rules correctly, that means the enemy needs at least 19 hits on their dispelling test to even start to affect the spell. The enemy mage has 6 dispelling and 6 magic, so they can’t possibly hope to succeed. On top of that, the attempt will cost them the drain of the 10-Force spell.

Is my understanding of the rules right? Is Dispelling really that weak?