I started over a couple times. Favorite party so far:
Insectoid Knight (Quick & Chitin) Heavy Weapons/Heavy Armor
Lizardman Rogue (Endure Elements & Agile) Light Weapons/Light Armor/Dodge
Ratling Alchemist (Mutation & Agile) Missile Weapons/Alchemy
Human Wizard (Fast Learner & Skilled) Concentration/Air Magic/Water Magic
Started over again with a couple tweaks. Kept the Insectoid Knight (Quick & Chitin) Heavy Weapons/Heavy Armor. Replaced the frontline rogue with a Minotaur Barbarian (Head Hunter & Martial for the accuracy) Heavy Weapons/Heavy Armor. The best weapons in the end game are all STR based heavy, and the most powerful weapons you get early game are STR based heavy as well, save for one dagger.
I moved the Lizardman Rogue to the back row and added a couple points of Accuracy to allow for light weapon attacks from the back row.
The Human Wizard I changed to a Human Alchemist. I realized when approaching mid-game that with the Human Fast Learner & Skilled I reached my skill goals very quickly and hadn't really had to use alchemy much. By making my Alchemist my caster I get to keep the herb duping and bomb making and I have a character I can start off with one point of alchemy in place of water. Beeline for Invisibility and use that with my back rank rogue backstabbing, then take water and alchemy later on.
With this setup I get two heavy plate wearers in the front for better survivability and make better use of equipment. I found both missile and firearms to be lackluster. You can get the second best bow in the game in the third zone and it's as good as the firearm you get in the fourth zone, but you can't re-use ammo for firearms so it's not worth it. Having a rogue up front wasn't as viable as in Grimrock 1 since there is no set of evasion gear. You have to go a minimum of light armor on the front ranks, extremely preferable to go heavy armor, and there are several really nice sets of heavy armor with good set bonuses. The dex outfit you want your rogue in to maximize damage doesn't require any armor use, so you put the two skill points in Accuracy instead of Armor to attack from the back rank and you get a nice additional accuracy bonus to boot.