I also struggled with Wyll to begin with, partly because (as per a separate discussion from a little while back) he’s not my favourite character, but also because he always seemed to miss and I made the mistake of trying have him use a rapier. Once I discovered the hex + eldritch blast classic warlock combo, selected the agonising blast improvement, boosted his CHA at level 4 and started making more use of his imp familiar for scouting, I found him more effective, and now often take him along and am slowly getting to grips with the different ways warlocks can be built and think it seems like a really fun class.
I had the same problem with Wyll in combat at first. I also had him use a rapier because, well, he is known as the Blade of Frontiers. An excellent swordsman, not a wizard or sorcerer (I don't think a lot of people would publicly declare themselves warlocks). I don't know if the average inhabitant of Faerûn can distinguish between wizard/sorcerer and warlock spells, but either way: wouldn't it have been easier for Wyll to pose as a wizard or sorcerer? Eldritch blast is not very subtle, people
might notice it...
With the hex/eldritch blast combo and agonizing blast, Wyll can keep up in battle very well, though it still feels a bit weird to not have him use his rapier at all.
I really like to have him in my party, he and my characters will agree on most issues, and I believe him that he sincerely wants to help others. He has his flaws, like every other companion (and my Tavs), but I think that makes him a much more complex and interesting character.
My current party consists of Wyll, Shadowheart, Astarion (Arcane Trickster) and my Wild Magic Sorcerer (I can't stop playing them), and it works really well.
But I haven't had a party composition yet that did not work. Sometimes it was a bit more challenging, but no matter how "weird" my party was, it was definitely possible to win a fight or achieve quest goals.
I do not choose my party members depending on their class or stats, but depending on which interactions I would like to have (e.g. a friendly rivalry between my sorcerer and Gale, the conflict between Lae'zel and Shadowheart,..) and what fits best for story reasons (having Wyll in my party for the goblin camp, Lae'zel for the Githyanki patrol etc.).
My focus is on interactions with my party and on a story, dialogues with companions are always my favourite part in an RPG. I like being able to concentrate on this and to not having to choose my companions dependent on which role/class is missing in my group.
Laezel with Shadowheart- the conflict between them is great
I can only agree. I wonder if these two will ever get to the point where they at least respect each other

Based on who is most fun in the party with great comments and voice barks.
Astarion - plus his VA is fantastic
I agree once more, the voice acting is phenomenal, I think Neil Newbon had a lot of fun playing Astarion (I think all the voice acting in BG3 is fantastic).
I almost always have Astarion in my party - although he is definitely not the nicest person around, I think he is the most entertaining one. And I think, like each of our companions, he is a quite complex character. I wonder which influence this whole "adventure" and the interaction with our player character will have on him.