Having leveled both I can understand how they feel "similar" because of the cast time and having a ranged physical damage weapon. But their playstyles are very different, Mch has RNG and combos, Brd has less rng, an extra dot, etc.

That being said however, while GB/WM are here to stay, I do feel that the complaint that brd/mch both have such a drastic playstyle adjustment that completely changes how they play after 50+ levels is a perfectly valid one.