Hoo boy, that mission gave me a hard time back than, too (and just recently, doing it in Hard Mode). For a first timer, if you try to fight the whole lot at the bonus at once, you'll get most likely your rear end handed to you on a silver platter.
As mentioned before, the "whole lot" is actually two groups with two Dolyaks each. They can be seperated from each other, and that is what you should attempt to do. It is a little tricky.
Now for the pulling part... Use the henchmen control flag to make your henches stay back. They should be about one and a half aggro circles away from the opponent you want to pull. Then aggro the closest of the opponents. This can be done by simply walking close enough so that he's inside your aggro zone, or more elegantly by using a long bow or flat bow (which have a range that is larger than the aggro circle). Immediately after the opponent has noticed you (or after you have fired the arrow, you don't have to wait till it hits) start walking backwards. Moving backwards is slower than forward, which means the opponents will slowly catch up with you. This makes it less likely for them to break aggro as you move away from them. Take a look at the red dots on the radar. How many are following you? If it is the whole lot, turn around and run! Flag your henchies further away. Once you have moved far enough they will lose aggro and return to their initial position and you can try again.
If the pull went right and only one of the groups is following, slowly lead them back to your waiting henchies. Immediately focus fire on one of the Dolyaks.
Note that if you didn't pull the group far enough, the Dolyaks from the other group may notice their comrade being in distress and come to his aid, meaning you'll have both groups on your throat again. So make sure you have sufficient distance from the other group before you start the fight. It will still be tough, but two Dolyaks at once are doable while four at once are simply impossible.
Also note: Clear that place before you talk to the dwarf in the cave to obtain the bonus. Otherwise he'll follow you to the place and will very likely foil your attempts at pulling (he'll not stay back with the henchies).
