Does this sound normal?

[JAZZCNC]

Even 60Vdc isn't enough to reliably run 34's in my view.
I know I'm talking of a mill with gibs here and routers are looser running, but still., I could not get my 1080oz reliably above 450rpm (2250mm/min).
I've bought a new driver for that particular motor (110vdc/80Vac) and upping to 80Vdc as a tester to see if there's any increase in performance. (Will be a while yet, still building new control box).
Will eventually go all AC.

Yes, I agree but in this case, with small Nm NEMA 34's like fitted on this machine then 60Vdc or more should get them to close 1000rpm. It's a combo of 5mm and low rpm which cripples the speed.

Will eventually go all AC.

Don't get hung up on AC, the only advantage is you don't have to mess around building DC PSU's. Even with AC power the drives convert this to DC for the motors.