This'll be a close fight.

Keep it up

You keep up your strategy. At the rate she's healing him, she'll run out soon. And at the rate your MP is refilling, you won't have to worry about it running out anytime soon.

You keep the charade up for a while until an unfamiliar screen pops up.

Temporary skills aquired:

Bash: 5 MP bashes the target with club, shield, or similar object. May inflict stun. Deals physical damage.
Compatible

Defense stance: 5 MP raises shield to prepare for an incoming blow. Halves damage.
Incompatible

Looks like you gained a skill. The tank ran out of MP first.

Your illusion spell wears off again and you try a different approach. You run straight up to him and bash him with your staff. His eyes widen as you see him realize the loss of his skill. It did almost no damage, but he pauses long enough for you to cast illusion again unharmed.

He gets sloppy from that point on and, before long, he disappears in a shatter of light.

You hear your level up ding but don't have time to check it as the healer turns and runs.

You chase after her and run smack dab into an invisible wall. Huh, if an invisible man runs into an invisible wall and no one's around to see it....