The reason Spellsingers have a large part of the Bardic ability 'pie' is because you folks chose to remove a Pre and fold the vast majority of its abilities into SS. This kinda made SS the more powerful of the two and most migrated into that Pre. The reason most 'healing' bards are in SS is most likely because healing in DDO has almost always drawn folks that place primary emphasis on the spell casting attribute of the class. If they wanted to CC primarily there was little to no power loss in that area if they tossed healing on top as an added bonus. CHA worked fine for both goals. For WC, most folks built for melee and pumping up the spellcasting side of the equation is a lot harder considering the demands melee is placing on ability scores and feats. Healing doesn't fit naturally into what WC is in the game currently.
It sounds like you all decided to essentially make SS the casting tree and SB the melee tree. At some point you remembered Bard had a melee tree (such as it is) and are now trying to find a role for it since you gave its purpose away to the new tree. My suggestion is that if you want a third tree to be healing then you need to delete, rework and rename the Warchanter
tree. Warchanter has never been the place you go to be a healer. The two have never been linked in DDO in any way, shape or form. Warchanter has largely been where folks went if they wanted a gish type character. That is probably going to be Swashbuckler now.
I have read a lot of comments prior to this one expressing a hope that WC could continue on as a place for melee bards that prefer twf and thf. I really do not see that happening the way it has been explained so far. Bards get no additional feats so that is 7 up 'til lvl 20. If you want to be a TWF type you need: TWF, ITWF, GTWF, IC whatever, PA, Cleave and G. Cleave. No room there for any metamagics. There is a bit more room in THF: PA, Cleave, G. Cleave and IC whatever, assuming you are willing to part with the THF feats. Ability scores demand Str and Con for THF and TWF needs Dex too. Where do they get the points for Cha too? Now when a melee bard shows up in a group with a THF or two weapons there will be an expectation they are healers too and I just do not see how they do both in epic levels without more feats and spell points.
Healing makes a lot more sense for a casting bard. SS is going to be the casting Pre. Ergo SS should be the healing spec. That or just remove WC and build a third tree that is the healing tree just like Cleric has a Damage, Healing and Fighting tree.