The Doctor of Z7 is just like the Doctor from Sonny 1. You have to use Subversion on his heal. Start off with a bit of damage, the use Subversion. Hopefully you'll catch his heal. As a bio, best thing to do next is to use Crystallize (2/3) to keep him stunned for 6 turns. Use Subversion when he comes out of the stun and you should catch his heal again. Repeat this until he's dead.
Note: Do NOT use Roald. If he stuns when you Subversion, you'll miss the heal and the Doctor will be up 500k HP.
Skill Bar: 1x Shadow Blend 2x Agile Exposure 1x Withdrawal 1x Toxicant Form 2x Slash 1x Predator Form Note: Predator Form and the second Agile Exposure are mostly useless, but there's no reason not to take them, as you might want to use one occasionally.
Usage: You have two combos: Toxicant Form->Shadow Blend->Agile Exposure->Withdrawal This is your main damage combo (the "nuke," as we call it), and with the suggested gear it will do over 37k damage to another level 30. Agile Exposure->Slash, repeat This is the in-between nuke combo. The damage is not that great, especially against higher levels as piercing won't have as great an effect on criticals. However, it should still do around 11k over the four turns against a level 30.
For Z7, I switched to my PvP build which trades 4/4 Slash for 3/3 Crystallize (and 1/4 Slash as a prereq for Withdrawal). Stuns are invaluable in fighting the final bosses (and PvP opponents).
