That ability feels like it has a lot of potential but it feels so clunky to use... If you use it and then swap attunement instantly, then swap attunement approximatively 4 seconds later, you never know without looking at your buff bar if the boon is still there. Will you fully attune? Dual attune? Who knows... That clunkyness is what makes me not pick it.
If the skill is to be kept as it is, I still think it needs to be changed:
That said, the most drastic (and in my opinion, better) change I might suggest is to straight up remove it, and compensate by integrating baseline shorter cooldowns in full attuning situations:
Basically, reduce the cooldown on the button that will make you fully attune, and reduce the cooldown on all attunements when you're already fully attuned.