I didn't think 5s was an issue. I never seem to have such an issue on cor, but I don't take the job THAT seriously I guess.
5sec is pretty nice on COR. Suppose you're shooting for double XIs - Legion, VW, setting up before some NM, etc. You get one XI, then you can bust at will trying to get your next XI (and get the base PR timer at 30sec instead of 60). It's really not uncommon at all to bust repeatedly trying to hit that second XI. 5sec times the multiple times you're busting adds up, even in the course of one buff cycle.
My timer is at 15sec with an XI up (5/5 Phantom Roll merits + Desultor), and I STILL sometimes have to wait a few seconds on a quick bust (PR+double up 1 or 2 times). Usually my timer is always ready though, and that's super helpful.
Not to mention, 45sec base rolls without an XI up is really nice too. Every second counts in getting those buffs sorted.