I wish I knew how much wits is required for secrets too.
As for other aspects, I recommend have as much wits as you need to have a desired position in the initiative order.
However, if you have a summoner, you can invest half of his attribute points into wits to be sure you find all the secrets. Summoners seem to have no primary attribute as all their damage is based on the Summoning ability.
Yeah, at least from what we can see in the Alpha build we have.
Plus it's cool to summon your minion and totems early in a fight

The AI seems to focus the totems a lot, ... maybe a bit too much.
I wish the AI had some kind of group tactics like let the ranged guys take care of totems instead of having the first in turn order spent time walking to it, smacking down and virtually wasting his turn.