Switching to a pool that supports the stratum protocol should reduce the number of rejections. An example for feathercoin is
www.multipool.inHowever my rejections are still around 3.5%, which is higher than I've had mining other coins, albeit at different pools.
EDIT: On a second check, you can stay at the same pool. Just use stratum+tcp://feathercoin.is-a-geek.com:3333 instead of the one you're currently using.