you could go for DS and sac your VW. the regen makes grinding fairly downtime-less. however, for me, you'd be better going up to DP in affliction, gettingall the drain tanking talents and using your imp as a mana battery
something like this
http://www.wowhead.com/?talent=IqMrVRbkqz
with this build i'd get as much +shadow damage as possible and burn em down quick. it's surprising how much you can get even in the 40s. oh, and grind on ogres whenever you can cos they're slow and so 'kitable'.