Warrior utility skills share banner cool down
That has nothing to do with banners or warrior skills. I have already reported to ArenaNet twice why skills get disabled a while ago.
You put “For Great Justice” in the same under water skill slot as Banner of Discipline in the normal skill slot (i.e. #8).
If you now use Banner of Discipline the game adds a cooldown to your Banner of Discipline skill and your under water skill at the same slot (“For Great Justice” at #8).
Now you try to switch your #7 skill to “For Great Justice” and it is on cooldown.
This stupid behavior is the reason why I put the worst skills into my under water bar to prevent such cooldowns.
Healing skill and elite skill are unaffected by that because you only have 1 slot for each type of skill.
Thanks for the tip Kejima, gonna test that underwater trick, need to prevent this from messing really important skills, specially for fractals.