I killed Thaurusan Turn 2 and his Wife Turn 1 with a nature build with bru'kan, Guff, and Lady Anacondra. completely free to play. if you do this combo right you go into the final fight with +8ish nature damage and can easily burst him down, I saw this thread existed before I played him, expected a challenge and was disappointed. it helped that everyone was ranged, so I didn't actually kill the Abomination until after both the Dwarves were dead.
can you say with what spells and upgrades?
I believe it was Brukan's +2 spell damage, double lightning bolt charm
Anacondra: +2 Nature Damage, +3/+10 to Trolls, Taurens, and Night Elves
Guff: +5 Spell Damage (Elite Reward).
obviously this exact setup can't be achieved every time, but You usually also don't need to kill him turn 2 before he even acts. I only felt the need to kill him so soon because I accidentally killed Moira on turn 1 by attacking her with anacondra. if you left her alive you could probably kill him much more leisurely