Iirc, the complaint was that Holos was good, but as a shield healer, we were supposed to be shielding more than healing - so this doubles down to what our job actually does. SGE was also lacking a competition to SCH in some high-end content due to Crit Adloquium Deployment Tactics when you needed big raw shields as Eukrasian Prognosis is both weaker and has no comparison. For raw survival when mitigation buffs and debuffs are already applied to the boss, having bigger shields are generally more viable due to diminishing gains on Mitigations. Holos getting a shield effect is good. The side effect is just making double shield compositions more appealing - but that's not due to the synergy of shield healers, but rather the lack of high outgoing damage that requires 'pure' healing. Encounter design issue.
The enmity on healers is kind of... ??? when tanks are the only ones who manage enmity at this point anyway. The enmity reduction isn't going to matter unless both tanks are dead and your DPS is somehow losing to you in enmity (not fully utilizing their DPS toolkit).
I don't think healers actually had enmity to worry about, so most of those changes are just fluff for most PvE content --- the only exception would possibly be doing the new Variant/Criterion dungeons since we still have no clue the exact nature of how much enmity those places should generate if they were supposed to provide a challenge to healers. Though... I don't think it really matters in retrospect, but we'll have to see.