I agree that there is significantly more spellcasters than rogues, rangers and warriors. Lae'zel is the only warrior in the group. I feel like Larian should of added a Paladin to complement her but then again Paladins also have magic. Astarion is the only rogue but he's an arcana rogue by default. He should of been given mostly rogue attributes instead of giving him spells. Astarion should also be the only one who can picks locks unless you choose to pick ranger for your character or a rogue. As for spell caster companions, you have three, a cleric, a warlock and a wizard. I'm not sure what the abilities of classes are in DnD but I notice that Wizards and Sorceror have pretty much the same abilities minutes a select few. I also feel that Wizards should not be the only one that can learn spells. I think that is unfair to Warlocks, Clerics and Sorcerors. In my opinion, the game doesn't have to be 100% DnD just based on it is fine. DnD is based on existing lore, they just tweak it for their own. So, Larian can also do the same for a video game.
You know, that you can choose the subclasses of your companions? Astarion is only an arcane trickster, If you choose it that way. You can make him a thief and then he hasn't a single spell on him. It's up to you
About the topic: It's true, that we have a lot of spellcasting classes and my characters add to the pile, since I don't play fighters. But I never had a problem, beating the game anyway. I often use my character, Shadowheart, Gale and Wyll and just bring the enemies down with spells.
