I ran a combat a while back where one of the monsters had a fairly strong stun ability. One of the players spent pretty much the entire combat twiddling his thumbs. Since then I’ve avoided stuns and dominates are even worse. I like this proposal by Sly Flourish: Making Stun and Dominate Not Suck.
…stun effects now result in -2 to defenses (-4 at the epic tier) and give vulnerability 5 per tier.
(A dominated creature) immediately moves its speed and makes an at-will attack against the closest ally with a +5 bonus to damage per tier.
Depending on where my players go, they may also run up against petrification effects. I’m thinking of making those stun + immobilized. I’ll have to see if that’s too weak or too harsh – a melee character suffers a lot while a ranged character doesn’t suffer much.