Rogue has better instant burst, but a feral has far more survivability and can hit much harder then a rogue if given the time to build up the needed combo points.
What is the proc rate on crippling poison? Is it 20% per hit?
Hmm, what do you crit with a 5cb-Ferobite with Tiger's Fury and Savage Roar for? (and how long does it take to build all that up? )
My highest crit on my belf-combat rogue was 1.4k Evis, took about 20seconds as I was up against a resto druid that didn't hit me, got to restealth once but it sure felt good to 2-shot him afterwards (450 Ambush+1.4k Evis)