Well, I'm inclined towards a percentile system because it's more efficient. However, as Darksheare points out, trolls have low hit points, so you might use a d4 for their hp, representing half a hit die on a d8. Also to be factored in is the fact that trolls regenerate, so even when you kill them on one thread they regenerate and reappear on another, per the cosmic law connecting the UT to all other threads on FR.
Gosh, I didn't know the UT HAD a Cosmic Law!
I guess if I wear making a troll, i'd roll a D4 and =1.
That wasy you get some variance, and the critter willl require one decent stroke to kill.
In MY world, trolls are much tougher, but they also tend to be decent people ala "Shrek"
JUST the guy you want to knock down the door in the chaos nest!