chanter are beast. they can solo the game well others can to but they are not weak. You may not find them fun some did some didnt but they are not weak.
No you dont need certain attributes. this is a roleplaying game you dont get to pass every check yourself. there are checks for every attribute so you cant possibly have them all high (unless you meta game i suppose but thats not the point) you find a role for your character and play it out. That is the definition of choice you can have x attribute high or y attribute high so choose one. I hope they stress this more in the next game and i think they will with all the new skills they are adding. Its good you dont get to unlock every piece of content in a roleplaying game. It means there are actual choices to be made on how you build your character.
That wizards are clearly better as melee is not true either. I have had dps leading wizards with wands or scepters. And they are monsters at cc.
I am sorry your experience was off but balance wasn't one of the issues of pillars in fact there are whole threads devoted to hating on josh for too much balance which I don't agree with fyi.
Chanters would only become useful if specific either invocations or phrases were carefully selected on each level upgrade, otherwise it was easy to make the build underperform and some of the phrases and even invocations were not very useful at certain levels (this happened on other classes too, but I felt chanters suffered more of this than other classes).
The wizard damage dealing and control build is viable and powerful, but overall the melee wizard I felt was overpowered, level 1 spell of wizard with the staff was simply much more powerful than any other level one spell and remain as such for a long time. Later on the lance weapon spell i think on level 8 or so made the wizard so powerful than the rest of the spell from there on, were really not needed. It felt odd wizards would eventually become almost front line fighters, typically you would expect them to be fragile and third row damage dealers or crowd control type.
Attributes checks, could be handled in another way, which could still give you a chance to pass them, without having to go against the builds you are trying to create, I feel that is still an area of opportunity for obsidian to explore and improve.
I feel balancing is still needed since too many classes had many talents/abilities that underperform while other were too overpowered. Correct balancing is hard to achieve and will most likely also be needed in deadfire, since it is hard to predict how people will mix talents/abilities and now even classes in ways that might make a character too overpowered, or make a class underperfom and therefore rarely used by the users.
Finally, I hope we are able to fully customize the story companions, since early on pillars of eternity you had to choose between going for an easier game mode or enjoying you companions and their backstory.