Brandedblade mostly covered it. But just to give you an example - It didn't matter when SE doubled Bole's potency from 10% to 20% mitigation. Even though this put it on par, quite literally, with tank cooldowns. It was very powerful, but power wasn't the problem.

Because of RNG, you could never count on having it for any given tankbuster or raidbuster. Thus, you always had to plan on a regular cooldown for these powerful attacks.

DPS buffs, by contrast, are always useful. More useful on a burst window, but still helpful anywhere. Even if SE just deleted the Balance, the Bole would have never been considered useful due to its unreliability. And, ultimately - even if refresh effects were still in the game - same issue with Ewer and so on. There are situations when you'd need it, but RNG means you can't reliably have it when it needed.