Burst > Nuke because Nuke has CD. Burst depends on how fast you can get your entire team to burst, and if you're doing it right, you can burst as fast as if not faster than a Nuke's CD would tick. Obviously, by burst I mean FB.

Healing / Delay / Counter all goes to Mitigation.

Debuff is lowest priority because it is merely a necessity. Once you've achieved enough of it, there is no more room to grow. Long story short: Debuff = Low Ceiling. Raw Dmg Dealing abilities / buff = High Ceiling. You'd wanna increase that ceiling for your team as much as possible, this is why debuff has the least priority.