I don't understand how 2nd level PCs can possibly be going up against _trolls_ and surviving - with its claw attacks, bite and probable rend a troll is pretty much guaranteed to kill a 2nd level character _each round_ a fight goes on. Maybe you could break down what actually happens in these fights? Do the PCs always get to buff up & attack at a time of their choosing? Fights where the monsters attack the PCs are always much tougher in D&D than vice-versa.