...no, no - that is totally fine, when you factor in: a) this isn't a 1v1 game (so your run-ins with DPS AMs don't amount to much, I'm afraid) ; b) any class that has range, healing & damage capabilities is always going to trump a Choppa/Slayer in a 1v1 encounter; c) a guard and heals would negate these DoTs almost entirely (Choppa/Slayer are more group dependent than other MDPS, but that is also because they can dish out more hurt).
@Panzer
I do think Rampage could be looked at again, but my point was that if you see a Slayer using rampage, and you are a MDPS/Tank, you should either wait it out, or shatter it; standing toe-to-toe with him is asking to die.