This is the forum for helping you out if you're stuck or if you want to discuss the nitty gritty details of the dungeons within Mount Grimrock. Warning: forum contains spoilers!
You might have trouble finding enough quality daggers. I think there is only one of the most powerful weapon of each weapon type, so it's a good idea to spread the weapon skills around. Also, it's useful to have at least one long range character.
The same goes for armor sets. If you have two heavy tanks on the front line, only one of them is going to be in the heaviest armor set.
My idea for a similar concept was:
Front Line
Minotaur Fighter - Armor and Sword (Planned for heavy armor)
Lizard Rogue - Evasion + Unarmed (Lurker Set and Unarmed to the +20 evasion bonus)
Back Line
Human Rogue - Assassination + Dagger
Human Mage - Ice + Spellcraft
The basic idea is to freeze difficult targets with ice bolt, then rush behind them and backstab as much as possible.
The mage carries a spear in his off-hand so that he has something to contribute when he doesn't need to cast a spell. Even if he's not hitting for much, hitting at all can disrupt the target and prevent him from attacking you.