well devastation gives you 37 crit rating per stack, which is 1%crit rating, and it can be consumed by white hit. On top of it all not every hit that dont crit give you devastation buff, there is just chance to get it. so you might fire of 5 combos and get only 1 stack. Beside how many combos are you planing on hittig to get devastation buff to be really worth it? If you dont kill someone in 3-5 combos you will probably die anyway.
staggering blow on the other hand gives you 36% weapon dmg for 15 sec every time you hit it, debuf target, is relatively fast combo and if you feat hammer and anvil it can hit nice to.
Now back on topic, your comment about kd 3/1 is what i believe to be slight problem with mini games. Not sure if it is possible to get that score without playing certain style. It encourage certain players to look for easy targets, hide from fights, and run if about to kill and totally destroy team play.
If they show k/d from world pvp i dont mind, but im against it in minis.
Give all other kind of stats and that can improve mini games, k/d wont improve it a bit but will have opposite effect.