In my opinion its the blood deathknight and Tauron. They combo well because the life steal you get from the blood deathknight is immense. When it comes together with the +%5 extra health of the Tauron it makes you really hard to take down. The +%5 extra health also effecting +max health items is just the icing on the cake. Your extra herbalism also lets you easily get ingredients for potions that you can make to make you even more durable when you get alchemy under your Belt. The same things can be said about the dwarf blood deathknight too. If you want to play alliance you can use the dwarf insted of the Tauron with similar results.