Could you please tell me what level of healing you expect PLD to be capable of. There seem to be a lot of contradictions here. You advocate that you should be prioritizing heals as OT even while including below why a healer is far better suited for that job than PLD is... Further, you just questioned a healing OT PLD hanging out in Shield Oath in the Shield Oath > Heal Oath > Cure > back to Shield Oath example Cheraa gave a few posts ago but now seem to be advocating the option here? Do you want the Heal Oath to be just slightly better at curing than the other two, making them each in their own way viable options?
Bottom line from what I'm seeing, sorry to repeat: Whatever his output, he's only got single-target heals, a very small mana pool, and breaks combos upon starting any cast but Flash. As it stands PLD Sword Oath dps is higher over time than any healer's dps. It is lower than high-efficiency healer DPS abilities, but each healer only has 2-3 decent DoTs. I can see a PLD with decent healing (80+% to 110% of a real healer's Cure/Physic/Benefic - though that would by then call for Clemency modifications) healing maybe once or twice as healer DoTs are exhausting and a maybe bit more to time up with GB or GB + a combo while the healer filler casts, but beyond that, I can't imagine him being much use. While the healer's DoTs are ticking for some 100+ potency per 3 seconds, his Goring Blade is only doing 40 and his auto-attacks are debuffed and delayed. The healer has pet or regens ticking for another 150-230 (relative, pet untraited) potency per 3 seconds. No matter how I look at it, the PLD is sacrificing far more dps than the healer to put out miniscule amounts. That has situation use, sure, but it's almost never going to replace a healer in a way that raid dps itself would not have (the usual limiter of a solo-heal run).
Also, as long as the PLD isn't oGCD healing (like healers' handful of abilities), he CANNOT dps and heal at the same time. That in itself will limit his versatility at least as much as any need to stance-dance to heal.