Well, you guys are arguing about an appropriate backstory to match lvl 1 characters, but I can think of one example of a character, from the original games no less, that also started at a very low lvl despite claiming to be much more powerful than he is. Edwin. Yes, he had an overblown ego and was a humongous narcissist. But he was also a more or less aged red wizard (clearly out of academies back in Thay) who wanted to become a lich (and obviously it backfired everytime he tried), but I can't think of any lvl 2-4 (lvl you actually meet him at) wizard whose life mission is to become a lich. I mean: overachieving much?
But yeah, overall I agree with the general notion that especially Gale and his backstory feel totally out of place. I've complained about it quite a lot as well. Same goes for Karlach too. But Gale is this shining example of a very poorly written lvl 1 character. He seems more like Ammon Jerro to me (NWN2 btw) which you got to meet until much later in the game (end of act 2 no less). I remember Larian mentioned somewhere that they wanted the PC to meet Gale much later in the game... and they decided to include him so early cause 'his story and character are too awesome' well, they should've stuck with their original plan for him. With Karlach at least you meet her early, but she runs off to BG. Really hoping she's gonna stay that way. So when we finally get to recruit her and she scales to our level, judging by all the free exp scattered in act one she's most likely going to be lvl 6-8, what would be a lot more appropriate start for such a character. And as for Minsc.... oooof, wasn't he petrified for a really long time? I don't know how much petrification affects your skill, I guess it doesn't judging by the petrified drow in the Underdark (and Branwen in BG1)...
Please god no. I'm really hoping Karlach's talk right now is just a placeholder. Everything's already screwed up anyway, i don't wanna wait 'til Baldur's Gate to get a companion that doesn't (seem to) need a support group 'cause suddenly stuff needs to make sense.