In Oblivion, coming across a troll at low levels was something to fear, not only could they regenerate health, but they could easily outrun you. Yesterday I had a running battle with a troll in Oblivion from Bravil to Leyawiin... the svcka would just not give up.. I expended everything I had on him but I still ended up with broken weapons. In the end I had to camp on a rock like a coward and wait for dawn to make a run for it to Leyawiin. This was just 1 frickin troll!!!
In skyrim, they are just way too slow to be any kind of threat. So your getting your ass kicked? simply run away at the default jog speed. Oblivion trolls FTW... the only thing akin to them in Skyrim would be sabre cats.. which can easily run you down.