First off, if the Sorcerer is on a Disk then he is likely running Metal, not Death. If this is the case get some Magic Resistance on your more heavily armored units.
I think the best bet for dealing with a Troll Hoard lead by Throgg is Fire and avoidance. Bring a Level 1, Fire with a Power Stone and bring a Witch Hunter with a Brace of Pistols and the Ruby Ring. This way you can still run a Level 4, Life or Light. If you have to get into combat try to get a multi-charge off. You could also bog it down with a Steam Tank.
Good luck.