For best race for tanking, I would suggest go with a race with the most defensive racial trait to give you a little bit of edge in tanking. Strength and Stamina are easier to make up than defense. On Qeynos side, Human has 2 +3 defence traits. On Freeport side, Iksar has +3 defense trait where as troll has none. Ogre just like human has 2 +3 defensive racial trait.