Question! Did I screw up by making Ashe a Knight/TimeMage to fill role of healer? OP guide says that combo is good for heals, but I'm 15 hours in and she still has Cure.
My Fran is a KNI/TBM, and her and Balthier are my two main stay characters so I probably spent a solid 40-55 hours of the roughly 65 hours I took to finish the story with her in my party.
And I'd say yes... She was rarely a healer for me until endgame. In fact, I ended up using my SHI/FOE Balthier or KNI/MCN Vaan more often for healing because they both had superior Potion Lores, and Balthier and Vaan with Hi- or X-Potions was better than Fran in Heavy Armor with Cure/Cura. It wasn't until her Magick Lores and Channelings got up that Cura felt good enough as a main healer so for a large portion of the story I used my WHM's Cura, and then by the time I felt KNI/TBM got her MAG/MP up, my WHM (but not TBM) had Curaja.
That said, it's a great endgame healer/buffer. Curaja; Hastega; Bubble; Bravery and Faith; Berserk. She has a better combination of heals/buffs than a WHM for 'leveling' in any of the last two dungeons. Plus, stays alive easy with high EVA or Magic EVA from her shield and can spam Karkata confuse.
WHM/TBM would be even better of course and for endgame bosses I'll sometimes switch my KNI/TBM with my dedicated WHM. TBM goes good with any sort of melee-healer like KNI or MNK because TBM ain't that great for synergies or standalone but it goes good with classes that are already self-reliant and just want a bit of extra speed (Swiftness 3) or a few extra buffs (Time and Green), so any of the dps/tank classes that has OK potential to buff as well work well with it.
Even mid-story, and let's assume 'No Trial Items,' you can get Karkata pretty early and Haste/Berserk/Cura around the same time. She picks up a lot of utility that actually helps reduce the need for a healer. I never really felt like she was a "main healer" as you wanted, but she also made it so for a lot of encounters I didn't need one. She'll crowd control/buff your DPS better than a WHM.