You can't combine vital strike and cleave.
Dragon should move and then vital strike, if it's going to use it. And cleave is when they are at reach for your bite when it's longer than your other attacks. They aren't going to be used much, but they are options if they ever are needed.
vital strike and flyby attack are a nice nasty dragon combo..
And cleave can be useful when fighting a bunch of targets..like pcs and cohorts..and animal companions..etc.
Vital strike on the bite -- lots of extra damage if you're only making one attack.
Cleave lets you make your one attack on two targets next to each other (like, oh, an annoying wizard and his slightly less annoying familiar, or maybe the princess and the knight with the same bite). This lets you hit multiple targets without having to make a full attack.
They don't stack by RAW; they're both for situations where the dragon can't, or doesn't, want to make a full attack.
But either of them would stack with Flyby Attack.
(Dragon falls out of the clouds, does bite-and-snatch on two adjacent targets, casts a quickened invisibility sphere, and then flies off in a random direction. What does the rest of the party do?)
Ah, combining it with Flyby attack is the what it's meant for. Good dragon tactics involve using your mobility to stay out of harms way while destroying the opposition. I feel that Full attacks should only be used as a last resort.
