I only switch jewelry and emblem when I find myself tanking. And I don't swap more than one or two pieces of my armour sets, either. I basically go from 4/2 to 3/3 of GC/Mene., and that gives enough Tact Mastery combined with the Might from everything else to get well above 40% OGH. The only time I find it necessary to go heal spec is raids anyway, and then never as primary, so it's more than good enough.
(Although Captains make excellent healers for 3-mans, I prefer to tank those instead.)
That means that Hands of Healing needs the following changes:
Rally Cry is ungated. This is effectively true in Lead the Charge thanks to the usual 25%+ melee crit chance, and it also gives Hands of Healing symmetry with the other Capstones and ungated defeat responses.
Song Brother needs to drop -5% Healing Threat and replace it with +Tactical Mastery, which opens up the possibility of putting Song Brother on a tank - something extremely useful if a captain is running without Fellowship Brother.
Song Brother: Strength of Will needs to be scrapped, and replaced with something that is appealing to most of the group. Someone suggested +5% critical chance.
1) Rallying Cry should get a way to be when in HoH used when in Battle hardenned stance and no longer require defeat event so HoH would use RC instead of BoE.
I've suggested to make Now for wrath a Legendary trait that would also make Rallying Cry work that way.
2) & 3)
the capstone self buff need to be no matter the X-brother skill used and To Arm skill need to become defined by that self buff instead of the X-brother skills
all that will resolve the issues
HoH will place Shield-Bro on fellow and heal with inspire, SoW will buff incoming healing and To Arm will increase outgoing healing while HoH will keep self Song-Brother self buff.
now only issue would become the power issue so the Tank LoM Victory Banner should grant morale and HoH Hope Banner should grant Power instead.