The Witcher 2: Assassins of Kings

Finesse bugd?

I put 2 Greater Critical Mutegans in my training tree after i got impreg. to lvl 2 so i got 12% base Crit effect on everything, then i put 1 point in finesse and got 13% on all crits, put in another point in Finesse and now it is on 14%, but i am sure it reads +5% at LvL 1 Finesse and +15% on LvL 2 Finesse NOT +1% and +2%.

Is Finesse working fine or what?

It's working as intended. All critical effects bonuses from abilities and items MULTIPLY the base critical chance. So if you're using a weapon with a 20% freeze chance and have finesse 2, you get a 23% freeze chance, not a 35% chance. And yes, this makes finesse really lame in most cases.

Critical effects mutagens are (to my knowledge) the only exception to this; they ADD directly to the base chance.