Well, if the skill would become too powerful if it would become generally usable, then the solution should be to decrease the value of the debuff it provides. Although even for the extension of OFF, which provides -40% physical RR, I doubt that the value is too large, when you look at other skills like Thermite mine. But it can be reduced to something like 25%.
That’s just sad to hear, if that’s really the case. But there are skills that already behave like this one should. War cry applies some of its debuffs instantly, while others with a separate duration (like the damage and resistance reduction). Ravenous earth has its own duration, while the damage reduction from Decay a different one. This method of inner workings already exists in the game, for many skills. The problem is that this skill will remain broken if they don’t do something about it. And I have no problem ignoring its existence and focusing on all the other skills, but it won’t become useful and usable until it’s patched. And it’s a shame to have a few flaws in an otherwise flawless game. And some builds will never become even more powerful without the benefits that these skills can bring. All the classes have at least one RR debuf that gets applied without exceptions, except Arcanist.