Getting filtered in the Troll Hole.

[Przybylski]

Do I just need to kill the little summoner guy to end the boss fight with the big troll, or do I need to kill him too?

[Slid Studio]

You need to kill the large troll. The small summoner will also be killed when the large one dies. Or, you can kill the summoner at once if you find it irritating.
As with most of the bosses in the game, the most important strat is to keep your distance, so the elkhead-weapon can not reach you.

Good luck!

[Przybylski]

Finding it incredibly hard to dodge his weapon, but I'll keep trying.
Thanks!

[Slid Studio]

Yeah, to dodge it is pretty hard. You trow everything you got against the troll, and when it nears you, you run to the oppsite side (expect to be hit some) and just continue shooting it.
Sword, axe and then bow is the weapons I use.
Just do not let it come too near!