As an FYI, Elysium used Eos in their World First A3S clear (they had Selene out initial, switched to Eos after)
Printable View
The only use for dissipation I've found is for planned fairy switching with swift-cast up or coming off cooldown within the 30s, you going to be spending the mana anyway might as well get the 3 stacks as a bonus outside of this the ability is just poo, almost as bad as the original lightspeed. People saying otherwise are just wearing rose-colored shades, and need to take them off. Other than that is not useful at all, to reiterate the +20% only works on channeled spells doesn't apply to Indom/Lustrate, so that doesn't translate really well to burst better burst AoE healing(e.g. +240hp on a 1200hp succor isn't that much), the 20% extra to single target heals, adlo/physic(300/400), do not make up for the potency lost from Embrace (200).
Dissipation is used to swap fairies in fights while being rewarded for it. There's no use to use eos in phase 1 of A1S, but eos is very helpful in the second half of the fight for covenanting tankbusters and AOE healing if you don't run a WHM, and my comp doesn't.
So, You have Selene for two ATK speed increases > Dissipation to increase DPS (which returns ~2,700 mana via energy drains whereas fairy costs ~1,700 to summon) > eos for AOE healing/tankbusters
Also, after you summon the fairy, you immediately have aetherflow back up from CD, so you don't lose any mana whatsoever.
On A2S, dissipation allows for more energy drains/banes and it raises SCH DPS alot because of how high SCH dps is on AOE packs due to bane.
Keep in mind that SCH doesn't generally heal until ~59% hp on oppressor on A1S, and doesn't usually need to heal until around wave#7 out of 9 waves on A2S. Dissipation helps with managing DPS mana costs as well as allowing for more spotheal lustrates if needed, AND increasing overall DPS.
And this is the worst skill we have IMO.
To even begin with, you can't compare dissipation to divine seal or Synastry. We are completely different classes.
Divine seal is a staple of WHM which is a tool depended upon HEAVILY.
Synastry is one of ASTs only emergency CDs to increase HPS to catch up to manageable levels.
SCH does not even need Dissipation to function at all. We are complete without it. If you took away WHM's divine seal for instance, the class would be extremely underpowered.