From the pvp forum here...

Rets are still decent in 5's arena.
Not nearly as strong as they were last expansion.
But decent burst, with cooldowns.
And survivability.

However the change to Word of Glory, with a 20 sec cooldown, on test.
If that goes live, that will really hurt the composition.

4x DK's + 1x Pally > 4x Pallies + 1x DK.
At least for most of us.