1)Remember spells and hex's can be interupted, then the caster needs to make concentration checks, spell resistance monsters,mess with the witch's familar, silence spells, counterspell,feebleminds
2)Keep your monster out of the spells range or have monsters that can strike from a distance or sneak attacks...remember invivibility is your friend.
3)Protection from normal arrows, snatch arrows feat, or items that mimic these abitlies.
It's always remember if your players are enjoying themselves then you r running a good session, but sometimes you might need to be a little hard on them, raise the encounter level up just a little bit and make them work a little bit harder for it... :)