If you made it through all that rambling - good job and sorry! To attempt a summary - the battles in this game are more tightly balanced than most people think. The constraints employed to allow a large variety of characters to get through the game error to the side of ease. After the first couple levels Lonewolf gives you something like an effective level jump of +4/+5 at nearly any point in the game. The game isn't made to handle those kind of level differences in combat.
Spreading arguably less power through 4 characters creates a lot of fighting vulnerability. Those characters that go 5th and 7th in the turn order are liabilities. It is much better to concentrate damage into 2 characters that are 1st and 3rd in the order. They become untouchable.
Don't be sorry, I asked for it. Actually some stuff resonate with me, especially what you're saying with the fact that being 4 people makes you more vulnerable.
Interesting read, thanks.
I found the warrior + geomancer to be a weird OP build, I would assume an OP build would be around the same type of damage (magical or physical) but I'm assuming my knowledge of the game is not sufficient enough.