In order of importance:
1) Embrava's Duration -> 90 seconds is a huuuuuuuuge nerf and makes it so the spell cannot be maintained. If you can't maintain Embrava, you can't rely on it as a buff and any Haste it has is fairly useless.
2) Embrava's Haste -> 25% is a big nerf, no more Haste + Embrava to cap magic Haste. This is less of a nerf than the duration nerf, because the duration nerf already makes it so you won't be relying on Embrava as a buff.
3) Embrava losing Regain is kinda bad, mostly for Ranger, but it has a much smaller effect on melee in zerg situations than people seem to believe considering melee TP gain during zerg.
Changing Regain to Refresh, though, is marginally more useful than it would be if it had stayed as Regain probably. Embrava is no longer a zerg spell, it's a "Designed for times when you would also use Kaustra" spell. It gives a gimpy refresh and lowers your recast timers so that you can use your spells more often. Like, if you were going to try to stun lock something solo on scholar, you could Tabula Rasa, Embrava yourself, and you'd be sure to have lower recasts (Alacrity Spam + 25% Haste) and enough MP to do it (Refresh from Embrava).
It's just not useful as a melee buff anymore because it's too short (except for Haste, all other forms of melee buff are 5 minutes+) and too impotent (doesn't let people hit the Magic Haste cap). Strategically, a perfectly stacked Embrava removes the need for one March for one song rotation if you time it properly with Perpetuance and cast it twice during Tabula Rasa. Congrats, Embrava can now be valued at one Minuet (the replacement for that march). If we ever went back to mage soloing, though, I'm fairly confident Scholars would cast it on themselves if they used TR.