Most of them so called buff skills I just them adrenaline rushes because they short duration and usually self cast only.
A Buff will always been something that not only benefits many but has at least 30 seconds of duration with a very short or none existant cooldown.
But are their effects useless? Nope. Well, maybe a few of the Knights because of the amount Knights get plus how long it takes to active them, but not useless...more like annoying.