My experience is that, once you reach gatling guns, melee and mounted melee units become obsolete very fast. Gatling guns can take melee hits from fusiliers thanks to their high melee CS and their covering fire promotion, while having a RCS higher than the Riflemen's CS in the Modern Era. I think they need to be toned down, their power feel like a Modern Era unit instead of an Industrial Era one. Even Foreign Legions suffer more than you'd expect against them.
Machine guns do feel overtuned, considering how gatling guns are right now. I can't say much about bazookas at the moment, I haven't warred with them yet. My latest lategame was peaceful (for me, the rest of the world was burning).