Same difference, really. Like I said, it'll separate the goods from the not so goods. It seems to me that since it benefits both you and the ally who clicks, it's not just a personal buff, which seems to be how you're thinking of it. It's like tricks of the trade without any tier bonuses. As a rogue, I'm using that on cooldown so I can buff an ally. Raiding's about teamwork, so helping boost other people's damage is important too.
For the Ultraxion and Blackhorn encounters, even if you don't really get the full use of the buff, someone else is, and that someone else is helping to speed up damage done as a whole, so it's still a win. For spine, I haven't done heroic so I'm not sure how crazy it is to deal with the amalgamation at 9 stacks, but if they know what they're doing, they'd wait till the tendon.
Also remember that it's also only a 6 second buff (with two buffs per statue), so I don't think that it will be THAT important for your DPS. It's significant, but I don't think Blizzard designed this so not having the buff at the most opprotune times becomes a big DPS loss. Plus, numbers aren't finalized, so things can change.
The benefit is the ability to do both damage and healing at the same time, giving the player an interesting, yet still viable playstyle. If you don't like that, nobody's forcing you to play the spec