Recently accidentally queued into a 4v4 (because for whatever reason it will occasionally forget your selection/it never remembers it and I forget to change it now and then under the assumption that QoL was actually thought of) and it was 4 NB's against 3 DK and an NB on Domination.
The inherent holding ground advantage the DK team had over the NB team meant holding points was far easier on the DK team than the NB team.
Come to think of it, a lot of classes who have more utility in terms of stealth or movement are actually already handicapped against other classes when it comes to BG setups: Can't use streak while holding a relic, can't use stealth, (Can you use targeted attacks like charges to act as a gapcloser while holding a relic?), things like streak won't help you hold down an objective, but restoring your max hp and resources when you ult certainly will.
Maybe it could be interesting to introduce a lobby where it segregates players to fight against the same classes as themselves?