Figure out what the problem is and move to an area that solves it

If they are taking longer, figure out what the problem is (mobs too far apart, mobs have too much life, too much downtime) and move to an area that solves Hero Gold.

30-39: Drain Tank: Load the mob up on DoTs, send in the Succubus, and cast Drain Life while the mob beats on you, rinse and repeat.

40-49: Drain Tank, but instead of Life Tapping, use Dark Pact. A good rule of thumb is, DP only if your pet is over 50% mana, because if they run out it will slow your fighting time down.

The easiest way to do this is to turn off all auto-cast abilities on your Succubus, and remember to DPing during the fight (rather than after) as a good time-saver because your DoTs will help keep up the DPS.

50-59: The Drain Tanking gets even better now. By Demonic Sacrificing your pet, you are able to regen even more life per fight, keeping up with increasing monster damage, while still 'Tapping up to full mana whenever you want because of the passive regen.

60: You are now specced SM/DS, which is generally accepted to be best grinding spec. Do whatever killing you need to do, grind factions etc., and then respect to your high-level build of choice.