Xbox will never happen unless Microsoft drop the "Xbox only servers" mantra or requiring gold on top of a WoW sub.
And considering you can't even play F2P stuff on XB1 without a gold sub I find it highly unlikely they would let WoW on without requiring the Gold sub. As for 360 I somehow doubt WoW would have ran well on that personally back then.
As for one game being worse than the other. Highly subjective. I enjoy both personally.
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I doubt encounter design would suffer.
As for healing on PS4. Basically you just have to get used to d pad targeting. It gets easier over time as someone who heals with a White Mage on PS4 and PC using a controller.
It does sound a bit daunting in intensive environments but it's very easy to get used to from personal experience.