Eos affords much more benefit to AoE healing than Selene does. Fey Illumination massively buffs your Succor, and Rouse>Whispering Dawn is the single most potent AoE heal in the game besides Cure III, especially when buffed by Fey Illumination. It can really help if you're struggling at surving/recovering from raid AoE.
At level 54, you learn Indomitability, an instant-cast 400 potency heal, which makes it a lot easier.
It's not novelty AoE. It's significantly more powerful than Broil in the majority of dungeon pulls. It's a drastic gain to pps and dps to pack Blizzard II with you. Stoneskin is /never/ necessary to be on a Scholar. If you need additional weakness padding, just give that person an Adlo before the big damage spike. If you're deploying Adlo, it's already enough for them to survive, especially if it's crit or buffed by one or more of Defiance/Convalescence/Fey Illumination.
Those two horizontal bars are just buff trackers. I never click anything on them - the only buttons I use are the ones on the x-hotbar. I have 2 things for Aetherflow and then one on my main thing because I suck at tracking the AF cooldown, so it helps me not fail and miss it.
As far as SS pre-pull in dungeons - Adloquium has a shorter cast and a stronger effect in all situations. My i215 SCH can drop Adlos that are stronger than Stoneskin on a near i240 PLD. Completely worthless cross-class, imho, at least on Scholar.
I mean. As a Scholar, you only need 1 pre-pull GCD for Shadowflare followed by 4 other GCDs (B2>M>B1>[Bane]>M2) to be performing well enough in any trash pull. After that, I generally will Lustrate>Adlo the tank before going into Broil or B2 spam. Stoneskin wouldn't extend that margin by a reasonable enough amount to make me not need to drop cleric for an Adlo in a larger pull (I never drop in 3-4 mob pulls). It's a discrete difference - not a fluid one. More health is nice, but doesn't realistically change an encounter. I will never let my tank fall below 3k either way unless I get distracted, so it's really not changing anything, especially when 1 Stoneskin is quite literally 2 attacks from mobs - and in a mob pull of 6-7, that comes in three-fold every 3 seconds. :0