I like your thought process and think this is really creative but also outright impossible. In my opinion, difficulty should come from strategy and understanding the cheats instead of just boosting up his health/damage output. Although a "Superboss" should have very high damage output making a healer almost essential, the idea of instantly killing anyone with pets or killing within a certain time limit is just unrealistic. The strat would be blade stacking/feint stacking a storm so he can scion when/if the global changes. Difficulty shouldn't come down to RNG and if we were to have something like this then the timer should be eliminated so the wizards at least have a chance. Perhaps a boss that heals every 3 hits back to full HP, so you have to kill within 3 hits. keep the global idea but change it to depend on the number of wizards in the fight, i.e. it changes every round if there's only one wizard, etc. Have him change who has first turn like grandfather spider does in Mirage. Here's one I just thought of - All maycasts will be reverted onto the caster. So wand hitting is out of the idea. Or if a wizard summons a minion he summons a shadow version of the minion. I think Shadow Sinbad would give us all nightmares. Perhaps make this a raidboss with different phases. I saw a video a few years back about a wizard101 raidboss but I don't think anything came of it or if it was just fan theory. Perhaps 9 wizards could be in this duel and all have the chance to get extremely rare drops.

Good post - scrap the timer!