The bleak ones are filling in a lot of holes...and I don't really mind them. But just seems like there have been a lot in a row.
Well, the series is only 52 episodes long, they've got to get this whole plot crammed in somehow!
There's one series I have - "Lost Universe" - the first twelve episodes are almost all silly, light-hearted SF fun. Then it gets into the main story and goes dark most of the rest of the time, while still managing to have silly moments. I think FMA is shaping up the same way.