I shortened my list from 4 to 2 so now it's abcpool and btcguild and made abcpool the primary. I seem to be mining on both roughly equally.
I switched the pools so that btcguild is primary and re-ran. Same result: roughly equal mining on both pools.
On my setup (debian testing, cgminer compiled from git) my primary pool gets ~9/10 shares and the rest are distributed among the backup pools. This is while the heat is making the router I'm connected to act up, so the network is in generally bad shape from my point of view. IOW, even though some of the getworks get dropped, only about 10% of the shares go to backup pools.
It might be a good idea to investigate whether your setup isn't somehow problematic...