Hi ya'll,
I had a similar problem. The troll can hit hard enough to knock you into the 
low PV point range (causing unconsciousness or severe woundings.) If he turns 
out to be a bit too powerful, the solution I have found is reduce his ability 
to deal damage. The combat will still progress smoothly, the player will not 
be at as high a risk, and there will still be suspense as players debate 
whether to press the attack or play it safe. Also, don't forget ranged 
weapons. The arrow/bolt ones may not do much damage, but in the cave setting, 
opening up by throwing a military fork, then hacking with the sword is 
perfectly appropriate.
Lance