Actually seem that is the case, when I got a NPC with a safe-cracking ability on equal level than my PC I noticed that they have different success rate on the same object.
Another tip, rarely the percentages are exactly as the skill say (10m 25, 65, 75, 90 , 100). So, the characters are getting bonus/penalties from their attributes.

Strength adds very little to your ability to fight. Enough to notice it, but clearly not enough to justify spending lots of attribute points on Strength. Between moving faster and having more AP versus a ridiculously modest flat damage boost, your points are better spent elsewhere if you want to make a good melee fighter.

I'd say this is because this is an open roleplaying game in a traditional sense. It is YOUR responsibility to roleplay and create reasonable characters, not having the game artificially constrain you in ways that inhibit imaginative roleplaying. A strength 1 guy still carries a little short of half his body weight in gear on his back, with the right technique (Brute Force skill) it is not unthinkable that he too can kick down a brick wall or put a crowbar to a rusty padlock.

I wouldn't say it's overpowered. If her Intellect is 10, what are the rest of her stats? You have to sacrifice quite a lot, IMO, in order to max one attribute.

I haven't got into WL2 yet, but this sounds like it's a heritage issue from Wasteland 1 (IQ was the most important attribute). Therefore I like it, thumbs up from me :)!

yes, the system is the same as the Wasteland 1, though you don't use your attributes directly, only the skills. But as I said before, seem that your attributes contribute to your skills for the pecentage of success