And then BG2 gave you one thief, and killed him. So at least PoE continues that tradition. (the other three don't count, Jan's a freakin' gnome, come on.) Also, Safana was super important in BG1, as she guarded the tome of constitution, which was an important first stop on any mixmaxing journey.
I think PoE should have had at least 10 companions though, so you could make two fully different parties.
Why doesn't a gnome count? Jan was also a full caster and there was no obligation to kill Yoshimo (I often just left him behind on the way to Spellhold, the million xp you get for his heart is not the best reward for Yoshimo's trap field of brokenness.) You could also easily ignore Safana and still get the tome of Con, she wasn't intrinsic to that quest at all.
I think the choice to omit thieves here was explicitly tied to the swarms of thieves in BG and BG2.
But yeah, I do feel the characters are a bit weak, I like the personalities of the fighter and the ranger, but neither of them has had a very deep story yet (I'm in chapter 2): the ranger's quest doesn't make any sense
(A valuable hunter left her beloved family and hunter-gatherer tribe for five years to tell a reincarnation of a dead elder how the tribe is doing with no reason to do so other that "it's traditional and people will be happy" and no real way of knowing if the unimportant information she is passing to a totally uninterested party is still true or if everyone she loved was eaten by bears a few years ago?
Any reasonable and responsible parent of three would have long since made something up ("met him, he is the child of a fisherman and he was really happy to hear that our reindeer herds were doing well five years ago": what, are they going to send another person to double-check?) and returned to actual, important responsibilities, e.g. feeding the children and defending the homestead from polar bears or whatever.
She sacrificed her family happiness to accomplish nothing of significance to anyone, when she succeeds, all that will mean is that the reincarnated elder in question will be like "oh, I used to be a boreal dwarf? Neat!" while her tribe is going to throw her a pretty nice party.
All of this could be based on my lack of information, but the story doesn't ring very true. I'd believe it if it was an initiation/ coming of age quest for a young dwarf huntress, but she has a family depending on her, what mad tribe would send pillars of the community out such useless and dangerous adventures?)
and is written as if I am much further into the game than I am (she keeps referring to some villain i am apparently pursuing), while the fighter's story is stalled by the reputation gain necessary to proceed, so he is just chilling with me not saying anything. Kana is super likeable and his story actually progressed when I followed his plot, but now it has stalled again, and I cannot get it moving by talking to him. Durance is the one with the most conversations, and they are fairly interesting, but the fact that I need to be perpetually traveling with him is a little grating since sometimes I want to play with the druid instead (not that he has had anything meaningful to say besides random gross-out humor, which is fine, if kinda cliche for halfling/kender/etc archetypes).
Finally the mage, Aloth. He is OK as a support mage and he has that whole double personality thing going, but really? Everytime he wants to talk (the text bubble pop up), absolutely nothing is said. We make small talk, like he is the mailman and I am too polite to acknowledge that he has an obvious second soul in there with him.
I really miss the way companion conversations worked in Planescape torment, where it felt that the conversation trees would suddenly twist in a new direction and open up new possibilities, only on the basis of your (highly malleable) stats, opening new depths to the relationship with the npc and even new spells and powers. PoE seems more influenced by the gradual unfolding of a character narrative along with the main plot, like Neverwinter Nights 2.