There was a technique I liked that they mentioned, but didn't use as much as I'd like, in 4e solos, where they would have actions that were strictly a response to PC actions. Like when a PC flanks, the dragon gets a tail sweep attack that can knock them back, or aura effects that hit those that come within within range. Then it gets into a puzzle of figuring out what triggers what response, and avoiding those things, while they work down the HP.
There's also the model of the Minis-game versions of the gargantuan/colossal dragons, where they have several different initiatives, but separate actions, rather than whole turns, like a bite attack is one, a breath weapon would be another, a move is a third, etc.