I disagree that the Centaur is a bad unit or that it's in a bad spot or that it needs to come earlier. Well I generally disagree with this stupid trend in balancing discussions that everything needs to arrive earlier and every faction needs everything to be accessible, which has led to dumb buffs like Pgrens in T0.
Anyway, the Centaur imo is a victim of the current 1v1 meta, which is to just spam generalist mediums and support them with AT guns.
Another thing is, while Ostwind became murdermachine to the point where it had to had put a limit on affected entities, Centaur was getting nerf after nerf, falling to the level of performance in AI comparable to Cromwell at times and its low speed isn't helping the unit either, its higher armor over ostwind, ironically, helps exclusively against med generalist tanks.