I dunno. It's not necessarily overpowered, but it may simply be unsuitable for competitive play. It's so hard to make rules on when it would or wouldn't work, it ends up mostly arbitrary. And because being instakilled by mind control isn't a satisfying way to die, everyone will end up resisting it, unless they're already so weakened that it's little more than a finishing move. If you were to take out the ability to kill people with it and only use it to screw with them, it'd be far more usable.

Besides, you may find some problems with the Gamo Tan too, seeing as it takes effect instantly and is thus undodgeable. You could say that someone could jump out of it quickly to avoid damage, just like how sticking your hand in an oven very briefly doesn't hurt, but that brings up a problem with the wording. You say it heats up not just the air, but whatever is in the area, including human flesh. You could boil someone's heart, killing them instantly without a saving throw so to speak.