This is a side effect of all characters having the same point-buy amount and to a lesser extent the removal of fixed racial attribute scores. Characters like Minsc and Halsin should have really high strength based on how they look (and based on Minsc's stats in previous games) but their classes don't really get much benefit from high STR so unless you give them an increased point-buy amount it would just be gimping them. With how you can respec any character to be any class as well, there's just not alot of reason to use most of the later non-origin companions.
