You are indeed missing a very important ability:
Troll Healing Healing
If the troll is reduced to 0 hit points by an attack that does not deal acid or fire damage, it rises on its next turn (as a move action) with 10 hit points.
It means that trolls can almost always swing or charge on their next turn, unpeturbed by being dropped... or require a followup attack from an ally.
I've done a 4-PC adventure once against two encounters _full_ of trolls, including troll minions, that all had this ability, and we had only one PC who could do fire... as a single target ranged attack. And we didn't know we were running trolls ahead of time.
So, yeah, it can in fact suck