Arbitrary
Tranny Chaser
Yes. Foxfire, Sigil of Malice, and Pyromania are ultimates. Other ultimates include Terrify, Reckoning, Dazzle, Rune Prison, Whimsy, and Parrlay.Not as a rule, Zilean's was just particularly stupid in that it was 2 abilities for a straight damage effect that had no interaction or skill involvement whatsoever. Half the ones you listed create an interaction with your champion and I think all but one of them are Ultimates...?
Again, you keep saying no interaction. Q E Q only detonates the first bomb. The second bomb still takes four seconds to cook off. That's a whole bunch of time to act for your target and their teammates.