I took them out for my stealth rock/spikes guy
and Gliscor, because i've seen it stall better, i wanted to try a stall team also and dragons =P
And even your chancey outsped my Dragon Tails, (-6 priority move) with my speed at like 328, chansey with max 282? thats 40 speed higher, +6, I guess priority + beats speed +
Also, Hydreigon and Haxorus don't get Roost. or any recover moves.
I had Gliscor Dragonite and Salamence all running pretty much the same thing, except dragon tail. Originally i set up rocks/spikes then bring out my salamence and watch people die, I'm amazed that even with +6 and Max speed Ev's Dragon tail still was slower than all of your pokes. i thought the +6 and the -6 would cancel each other and go based purely on speed.