I've ended up in this position fairly often - heal spamming the mob, Final Sting goes off and the ongoing damage is so great, not even Bene or Tetra/Essential Dignity gets there in time. >_<
I've been on AST a lot, lately, so.... I've gotten to the point where I focus target the original spawning Orn hornet and Cel Opposition stun them when I see Final Sting. Every now and then I'm too late (as it takes a second or two after the initial flash, to take). I find even a swiftcasted Holy is too slow to do the same thing, though. :/
