Ok... here's the thing.... I really, really do not like the interrupt mechanic as currently implemented. Not as something that can happen from any attack. Interrupting spells in the process of casting - fine. Interrupting attacks, but using a spell or ability - fine. But this whole "any attack can interrupt any action" mechanic? Nuh-uh. Nope. Bad mechanic.
And here's why, from a game design standpoint. Interrupt, as currently implemented adds RNG to battle, but in a really unpredictable way that is hard to anticipate. Good, rewarding mechanics are all about giving the player various tool