It can be a significant dps loss over the course of a fight. The thing is hunters can provide it passivly with pets or warriors with a glyph. For a rogue it is a GCD where they are still auto attacking, would be better if it was a resto in your raid.
The FF provides no eclipse energy so not only does it waste your nature's grace and slows you down 2x but also takes away from a GCD, which for a caster can be alot more important when they can hit/crit from 300k-500k compared to a melee whose damage is mixed between white and special attack damage.
If you have no other options at ALL, yes it is a "raid" dps increase no matter what.
Glyph of Omens gives your FF 10 energy outside of eclipse. Casting this when pushing to lunar when you have left solar eclipse on either 0 or 5 energy, would cut one non-eclipse wrath from your rotation, which at GCD cap would mean you shorten your time spent casting to push to lunar is cut down by ~0.55 seconds with no haste buffs active.
Naturally, when this specific scenario isn't the case, you wouldn't cut any uneclipsed wraths from your rotation and thus lenghten your cycle by another global cooldown.
Ofcourse, this would mean you'd have to sacrifice another glyph, preferably Glyph of Rebirth since other members in your raid can provide the battlerez.
This glyph alos makes other of your utility abilities grant eclipse energy out of eclispe, such as solar beam, vortex, stun, roots, typhoon, etc.
I personally like to roll with this glyph on heroic Horridon where I'll be using FF to knock the dino away (FF is an omnidirectional spell, therefor macroing this to always go on the pink dino, is more beneficial over dotting it, since you won't be getting any SS procs from that target and the damage is wasted.), it is a nice small bonus for specific scenarios in pve, to be fair, arguably makes little difference at all.
Last edited by Rocketbear; 2013-08-25 at 12:56 PM.