The whole rotation is good but a couple of remarks are necessary to be done:
1) I don't think Broadcast appeals to me, especially if there're 30+ players online. Its entrances are too shor and narrow so it turns into a meat grinder sometimes. That's not a very good situation, as for me.
2) Pipeline is too moody imo
3) Showdown correlates to the point 1) I've mentioned above. It's not much fun for 30+ players - especially for a hardcore server you have.
My verdict: Ambush, Backlot, Bloc, Crash, Crossfire, District, Downpour, Overgrown, Pipeline, Strike and Chinatown are fine in any order you like.