So far in my experience (normal difficulty, full party):
1. Might - it's more damage
2. Intellect - AoE spells are devastatingly powerful, and this makes sure you can nail all of your enemies with them
3. Perception - Useful for both stopping enemy mages proactively, and the deflection bonus to stop melee attackers, therefore making this the best defensive oriented stat.
4. Dexterity - Honestly, I feel like the boost to action speed really isn't really worth it. Since action speed affects EVERYONE'S effectiveness, this is the sort of stat that, if it were good, you would want to pump on literally every character. Obsidian obviously balanced this by making it weak, that being the case.
5. Resolve - Concentration is rather meh, from what I've see so far. If you tank properly and position well you almost never have a use for it, since the only 1-2 people on your front line getting hit don't do as much damage as everyone else, anyway.
6. Constitution - Ok, so basically Con wastes half of its utility by granting health, which 1) doesn't matter if you're rolling over enemies 2) doesn't matter if you're NOT rolling over enemies, since then it must be a tough fight where you need utility NOW and not later. This is probably more useful on hard difficulty where camping is more restricted. That being said, might beats con by giving you 3% more healing, which increases your effective health even more significantly! Con seems blah.