I think contra definitely needs to be in the rotation.
Also, even though I like what you are doing with just rotating those couple maps… I think a shorter rotation is best simply because say I am one of the people that wants to play sk3; I could conceivable play for 8+ hours straight and never have that map show up, even though its in the rotation. I think you would be better off with a solid 10-12 map rotation, supplemented with weekly fun nights where you play some of the other maps. I will again suggest:
de_dust2
de_piranesi
de_inferno
de_tides @ 10 mins
de_cbble
de_dust2
de_cpl_mill
de_contra
de_season
scoutzknivez3 @ 10 mins (no stats)
cs_office
BUT thats just MY suggestion, of course. At least I don’t see strata, fire, or prodigy in your list, which is DEFINITELY an improvement right there 