Tony Vargas
Legend
I'm sure there's plenty of room for other abilities. Clerics get quite a bit of healing, and good armor proficiency, decent weapons, orisons and other, non-healing uses for channel divinity and spells. Healing may be of prime importance, but it clearly doesn't cost a lot of other abilities when balancing a class, so no worries on that front. I the warlord's healing contribution to a party is comparable to that of a Cleric, then they can stand in for eachother when one is inappropriate to the setting (such as Dark Sun), doesn't appeal to anyone at the table, or otherwise unavailable. Ideally, there should be a couple of other classes able to take up the 'band aid' burden, as well - the Bard and Druid have both had versions that could do so.I don't have a problem with warlord's healing, but I don't think it should be their primary asset. I would be disappointed if warlords get a "channel divinity" like ability; it defeats the purpose of different mechanics.
Each can also contribute the overall complexity of the game by doing so in a mechanically distinct fashion, of course.