I'd really like to help you. If you're taking too much damage, then maybe it's an Armor Class problem, coupled with a lack of terrain control, if you put grease down you can keep a lot of enemies from swamping you all at once. Barbarians are nice too, because they can be damage dealers and tank-y depending on what the party needs, try using a shield with your Barbarian and give him some other buffs to keep him around long enough for your artillery to do the damage.
Which fight in particular is giving you such trouble? Being able to take out Minthara, means you must be doing something right, if you're trying to clear out the goblin camp outside, that's a tall order for anyone.
