I haven't made any change to Dazed, and changed Stun to: Dazed and -5 to attack rolls. It's pretty straight forward, easy to remember, and leaves both players and monsters with plenty of options still. Second Wind, aid another, or just taking an at-will attack with -5 is plenty better than doing nothing.
And for the occasional (rare) solo or elite, I'll tack on immunity to daze or stun especially if the creature has high reliance on immediate or minor actions to function. I also use all sorts of funky mechanics like creatures with multiple standard actions, more than 2 action points, multiple initiatives, free interactions with environment, spawning/summoning powers, etc, whatever it takes to make a challenging and interesting encounter, and to keep players guessing.
And for the occasional (rare) solo or elite, I'll tack on immunity to daze or stun especially if the creature has high reliance on immediate or minor actions to function. I also use all sorts of funky mechanics like creatures with multiple standard actions, more than 2 action points, multiple initiatives, free interactions with environment, spawning/summoning powers, etc, whatever it takes to make a challenging and interesting encounter, and to keep players guessing.