For the first time, one of my parties decided to do the bandit camp "the hard way". Essentially, rather than try to infiltrate, they went for exterminate instead. This was likely not a brilliant choice in hind-sight. Primarily because instead of fighting all the bosses by themselves in an enclosed area, you fight them along-side the whole flipping camp, and that many archers makes magic use impossible.
The strategy, as it were, was to take out the hobgoblins at the temple ruin, then use it as a staging area. I sent in Maeri with invisibility alongside a skeleton warrior to act as bait. That part went according to plan. The squad start laying down sleep and grease. Then, the bosses all showed up... at once. Chill archers on one side, Blacktalon on the other, and three "wreck-it Ralphs" in the middle. I also learned that just because you can't walk through a forest area doesn't mean you can't fire through one. My party got perforated - forcing a reload.
Second attempt - draw them to a section of forest near the edge in the hopes of escaping when the battle got out of hand. This almost worked, but Aura fell to a sleep spell, and then a hail of arrows. Before Maeri could get to her, Isra went down and Sirene was completely surrounded - sad to say, I once more reloaded, I knew there was no way to pull this off without Aura and Isra.
Third (and mostly?) final attempt. This time, I decided to draw everyone to the edge of the forest, but I was a bit brighter about it. I kept Aura, Imoen, and Maeri invisible, again using a skeleton warrior as bait. However, this time I kept everyone near the edge of the forest. When the whole gang arrived, the visible party members chugged potions and went after two bosses at a time. When they were down, the party bailed back to a nearby forest to rest.
They repeated this cycle a few times, each time taking two more named bosses until they were down to the random, unnamed bandits, hobgoblins, etc. It took about week of game time with all the travel and sleeping, but eventually the party whittled down the remaining bad guys. FINALLY, everyone in the area was pushing up daisies or party of my party - except for a few stragglers in the tents and cave. A quick sweep left the whole place devoid of mercenaries.
Which left the main tent - now completely empty except for the prisoner, Ender Sai. That was almost strange, but I guess everyone that would have been in there was now dead. It was a bit anti-climactic to start chapter 4 that quietly.
That was an insane battle, and I don't really feel all that bad for breaking it up into multiple attacks like that. With "better calls for help", it was literally everyone in the bandit camp compressed into a small area of forest.