Have about 100 hrs in and have seen no issue with balance. I think having so many different ways to approach the game is a lot of fun. One of my favourite partial playthroughs was as as a warlock with Shadowheart and Astarion as my companions. In that playthrough I swapped out Shadowheart's armour and shield for leather only just for fun and as a way of making her less conspicuous as a Cleric. Obviously I was extremely careful in picking and choosing combat as I was extremely vulnerable to melee combat. Some fights and side quests had to be avoided and I chose an evil path ultimately bringing Goblin hell to the grove. Even with that weak party I was able to defeat the Druids though Astarion fell ( I don't use resurrect scrolls on my playthroughs).
I just love the variety on offer even in Act One.
Like I said before running a 4 member part with Caina a Ranger-knight Lae'zel, Wyl, Shadowheart. I do use resurrect scrolls. And since you don't how do you get rid of the one that has fallen in battle or do you just play on with the ones for which you have left and leave the fallen one in that spot?