With hunters I wouldn't worry about twinking the heck out of them.

I remember pretty much kicking butt on my one hunter in BG's. It was great being able to take down twink rogues. I was very frequently at the top of the table.

I did have a few occassions to play with two hunter friends - and we did great damage.

Now the thought of 5 hunters in perfect synch, with 5 pets is making me drool

Definitely do what you said - run the right instances, look for the crafted items and get them decentish gear.

I would also suggest trying your 3 warlocks (I would probably suggest affliction), just to keep incredibly mobile (hate those pesky rogues).

3 sets of dots and 3 shadowbolts if you've got time are gonna do some serious damage.

I would just suggest running towards a group of enemy- dot dot dot, tab target, dot dot dot, tab target, dot dot dot.... rinse... repeat.