Yes, the correct combination is the 3 locations, but, what do you do when the spider moves? Your trolls are stuck... how do they get from one side to the other? It turns into a web fest too.
I used to split up the 3 trolls so no matter where the spider is, at least one troll can hit them, but that takes a while.
Maybe I didn't try hard enough but I just didn't feel the 100+ rounds of combat was worth it for me. (well that was with the Viking/Warrior).
With my Soothsayer, I just figured it wasn't worth it.
Took me 24 rounds with losses and that was while using a lot of bears for heavy offense.
Yeah, only way to do it with 3 giants would be if you get lucky with a Call Colossus (which I incidentally did have).
Although I wonder if they are really the best choice?
It might be doable if the current game wasn't BROKEN with regards to archdemons NOT getting rage balls even if they score a kill.
Anyway, you'll see what i mean by no loss is not worth it if you try to beat the game.