To help you I will need to following information.
Party composition and skill usage and what level those skills are.
I will also need to know your level im assuming 5 or 6.
so example would be :
Jahan level 6 / hydrosophist 2 / areotheurge 1.
But I find if you approach from the river and then stay back and summon something closer to them to start the fight. then you cast firefly along the river so they have to move into a tiny space.
Use as many summons in the front of the hole you left. Use teleportation on the archers to get them to you faster and finish them off quick.
When your firefly is up again cast it the same place but try and cover the ground the zombie boars are standing on. Once they are set on fire they will try and run through the fire killing themselves.
Use as many stuns you have in your party on the range creatures you are facing.