My builds in no-recruiting mode (no spare characters specialized for support roles) are generally, listed in the order in which I try to max skills:
Berzerker: Madness, Flurry, Rage, Swiftness
Ranger: Sharpshooter, Rapid shot, Range focus, Black out the sun.
Healer: Aid, Blinding, Inspire, Bulk up.
Ice mage: Sleet, Blizzard, Ice splash, Ice shard (although I put a few points in Ice spear first)
Knight: Armor break (only to level 4), Swing, Sword training, Smash, Hard knock…
Dragon: Bite, Strength, Devour, Halitosis.
So, the smaller the party, the bigger emphasis on direct damage output
When playing with multiple characters in each class, it of course makes sense to go for specializations that are built more around traits. I can imagine that from 6 berzerkers, I’d go for 3 bleeders - Swiftness and Rage first. But the next two skills would again be Flurry and Madness, so no big deal.
With rangers, having a long-range bleeder set to target Strong makes sense. And I could also imagine a short-range, max poison and max damage skills build, again set to target strong and placed early.
Healers are probably the only class where I’d never bother with putting points into the two AoE attacks.
Ice mages are awesome damage dealers, but having one with maxed slow/freeze traits can be quite useful.
Knights - the armor-stripper with high damage skills is the obvious choice, but I could imagine a Stun specialist at start of killzone and Smash specialist at the end of it, especially with their NG+ swords to boost the appropriate skill. And since they wouldn’t really need to strip armor much, damage levelups would certainly happen.
Dragons are perhaps the most interesting, capable of fulfilling several roles - softener near spawn with maxxed Bite and poison, cleaner with maxxed Devour, AoE specialist with maxxed Roar and Fire Ball, all of them make sense and they’d all have some attack skills maxxed.