And so, after gaining the nigh-perfect understanding of the system, I can present the strongest party build:
1. Insectoid Battlemage - points into Dexterity & Vitality - Chitin Armor & Natural Armor - Concentration & Fire Magic
Level Ups: Fire > Fire > Concentration > Concentration > Armor > Armor > Armor > Armor > Water > Armor > Athletics > Athletics
Dex from the start because it's better in the long run - you don't need that much Energy on him but, once you gain 4 ranks in armor, those 5 evasion become more or less useful. Armor is crucial - protection is an all or nothing affair so you can't go lightly here. In the crystal set he'll have 150+ protection - now that's what counts. Athletics is simply to amplify the effect of those 150+ protection. And little magic here because he can cast all the best stuff anyway - fireburst, fire shield, force field, shield, darkness, darkbolt. He can also throw bombs - better to waste his time on that than anyone else's. And he'll use magical trinkets (like the crystal shield). Water Magic is for dispel - those pesky Air Elementals. If you find the dispel staff or ethereal dagger before that, it may be skipped and extra level can be put into Athletics. Or you might max out fire simply for the +50 resistance.
2. Lizardman Knight - points into Dexterity & Vitality - Endure Elements & Evasive - Armor & Light Weapons
Level Ups: Armor > Light > Light > Critical > Critical > Critical > Armor > Armor > Light > Light > Critical > Critical > Armor (+ Dodge > Dodge > Dodge from the skillbooks - it's your main damage dealer through the most of the game so you focus on him)
While on its own evasion is very weak, coupled with a good armor score it becomes rather strong. So that's what we're building here - you take the ability to wear the Reed armor & profit from them, them you enable your backstab, then you prepare to wear heavy armor as that switch is inevitable and you work on your DD capabilites afterwards. See, I dislike the backrow Rogue because he's not utilizing dexterity fully - he's gaining damage from it, but not the defensive capabilities. His evasion goes to waste. Here, yes, he'll have about 6 less damage per hand (which is not that crippling), but he's a great tank, especially after you dump a dozen or so of +DEX potions into him (which you totally should - this guy is a power nexus for your party).
3. Lizardman Fighter - points into Willpower & Dexterity - Endure Elements & Fast Metabolism - Heavy Weapons & Accuracy
Level UPs: Accuracy > Heavy > Heavy > Heavy > Heavy > Accuracy > Accuracy > Accuracy > Critical > Critical > Critical > Critical > Critical
Yeah, no strength, lol. See, in the end, those 3.75 damage lost from the 5 strength don't matter that much - you want strength, you just gulp a rage potion (they stack with each other, btw). But to do that, you need accuracy which is what we're building here. And willpower is good in the combination with the fast metabolism - we simply can slamdunk more often. Throw in an Archmage set (best set for the fighter, lol) and you're all set up.
4. Lizardman Alchemist - points into Strength & Dexterity - Endure Elements & Aggressive - Throwing Weapons & Alchemy
Level Ups: Throwing > Throwing > Throwing > Throwing > Alchemy > Alchemy > Alchemy > Alchemy > Accuracy > Accuracy > Critical > Critical > Critical
Not as good as the minotaur rogue in terms of DPS, but Alch just gives you way too much extra potions to ignore him. And he's still a decent source of DPS.
Btw, it's one insectoid + 3 lizard because you'll find enough + protection items to protect one character reliably, so 4 lizards are probably an overkill.