Re: Whats best merc for fury Dru?
A Defiance one might actually work if you use Ribcracker - which gives you extra defense - and Fortitude, for the chilling armor bonus. The Defiance, Chilling Armor and Ribcracker's defense bonus can amount up to quite a lot of defense, actually. However Defense is usually skippable in PvM.
My personal choice tends to be a Might Merc with Reaper's Toll, you just can't beat the crowd control and damage increase Decrep gives you. This guy is by far the most effective, IMO.
For style points you can get a Rogue with Faith (really funny if you're using Tomb Reaver yourself, since 20% of your + Merc's kills will result in skeletons being spawn) or a Barb Merc with Lawbringer or Azurewrath.