I don't think it will ever be too late to change things. Look at their current design direction: They changed a system of profession specific boons into a somewhat homogenized alac+quickness system over the course of 1-2 years. They could do something similar again if it doesn't work out the way they want.

But one other thing came to my mind. I think perma boons you have to spec into might fulfill the offensive support fantasy better than a time-limited boon. With perma boons you associate the boon with your party or the boon provider specifically, while a temporary boon feels more like a property/mechanic of the enounter you're fighting. With perma boons you have to stay close to your group for example, while a temporary boon would only requires you to stack on boon application, like many other boss mechanics. Maybe that's just me, but being the boon guy sounds more fun than being the one to press a certain button at some point, provided boon support gameplay is fun as well of course.