Agree on ba_wowarena.
Another map that should go is aim_dust2_long1. It's not really an aim map, should be de_, but it's clearly not designed for wcs. It's way too easy to get behind walls and under the map with no texture on the outside and able to shoot others easy through floor/walls.
I'd prefer to see more objective maps in the rotation. Right now we don't play that many bombing maps and even less hostage maps (though rescuing is pretty hard on wcs).
Maps that I personally don't like are things like scoutshine, all awp maps, fy_wcs_01_v1, aim_ak. There's probably more but they aren't in the rotation that much and I don't remember the name.