I've started a number of playthroughs as a wood elf chanter.
It's fairly remarkable what a difference having even one hireling in a party can make. I actually had to restart my first game on normal difficulty because I hired a 2H barbarian to go with my chanter. Both of these created characters each out-damaged the rest of the party combined (Aloth, Eder, Durance, Kana Rua). I restarted again, adding Pallegina to the team in place of the barbarian, and things felt balanced again.
In the new play-through, my chanter (pistol) once again does thrice the damage of the rest of the party, although I suspect Pallegina with her blunderbuss flames of devotion alpha strike followed 2H melee might start creeping up eventually. Without actually trying it, I think a better optimized all-hireling group would absolutely steamroll the game on normal difficulty, and would probably have an easier time on hard than playing medium with your companions.
Of the provided companions, Eder seems to do his job fairly adequately, and Kana Rua (Hammer and Shield) is a nice compliment, despite his incantations being of little use in shorter fights. Durance is a solid contributor, but that may simply be my ignorance of how much better a hireling priest would do in his place. Pallegina isn't really fitting in well. She offtanks fine I suppose, but I'm sure she would be a lot better off with high might to go with her FoD and blunderbuss. Aloth sucks all around. I don't need a control mage in the party with a PC chanter, what I'd really like from a wizard is occasional burst DPS on tougher encounters. Sadly, Sagani seems even worse, and Hiravias doesn't seem to contribute as much banter.
Pretty underwhelming. Every BG2 character had a stat line that was somewhat workable... save perhaps Cernd and Aerie. There's certianly no Minsc, Edwin, Ajantis, or Kivan here. Pretty disappointing that they chose to balance normal around trash-tier companions.