With the way the talent trees work, it would be a perfect way to get rid of healing plate gear. Just introduce a starter skill for investing your first point into Holy that's something like:

Sacred Armor
Increases the armor contribution from cloth items by 170%.

Bam, no more need to make plate gear with healing stats on it and instead paladins will compete with priests (or change it to leather and have them compete with druids). Just make it so paladins also gain armor mastery from wearing cloth.

We want paladins to look like paladins. We make raid and PvP gear sets that look paladin-like and have paladin names. We want players who see a healer from across Arathi to be able to recognize it as a paladin. Putting (level 40+) paladins in anything other than plate is something we are unlikely to ever do.