The trolls are human sized... 2 m at most, an Ogre is atleast 3-4 m in size.
Trolls can regenerate but they aren't that much stronger than a human, definately weaker than an Orc and an Ogre turns an Orc into a bloody spot with a single hit in most fantasy lores.
Also let's not forget that Tinkerer displays the MC as an unskilled adventurer that wins most fights by surprising his enemies and fight overhelming numbers in small groups.
He struggles seriously against single powerfull enemies and still uses dirty tricks most of the time to get an advantage... the MC chooses his battles and chose not to fight Dolf directly... I am not sure about the reason aside of cowardise.
I can't see the MC going Full Hero in order to deal with a Monster like Dolf for any reason... maybe if he had the backing of all the guards of weirdwood, but not in a 1 on 1