I think it's funny you consider 2.1 overly slanted towards gunner engi marine borg, when the next 2 most common classes have gotten shafted since 2.1. Recon is nowhere near as useful as it was in 2.1, and arsonist lost a second on his freeze time.
As for the 4 main classes changing since then, marine got good hyperblaster, gunner got a better mega, and borg/engi changes more or less balanced each other out.