You are complaning for insignificant buffs that happen in an already dead content. Anyone who is still progressing is really late to the party, anyone who still hasn't got their legendary cloak is already late to the party... really really late. This buff could be a problem one month after patch release, but not now.
But anyway, i agree that the implementation is wrong. At this point in time both buffs should be permanent. And if in the future they have something similar to the cloak i also agree that there should be some kind of shortcut to make it easier for alts, just as you get a valor buff when you cap with one character.