I doubt charachters r still in development, instead they r tweaking balance for both gameplay and server load. Given the nature of both, most companies either do a massive (open) beta test that runs for a long time or several short closed tests that grow.
I expect gearbox to do two large betas, one in feb(for preliminary testing) and one in april( for hype).
Side note: the division beta is the end of thus month supposedly.

