Templars, Paladins, Clerics, etc, all have one thing in common: they can cast healing spells while in full plate armor, with no penalty. A Templar wearing heavy armor should get the same magic bonuses as a mage wearing light armor. That is what makes them different.
1) give the magicka regen bonuses to heavy armor for Templars
Templars are healers, so they should have an "affinity" for healing objects, like staffs. Any object that boosts healing, has a 15% buff if it is a Templar. Conversely, Templars, Paladins, etc, are not good at Destructive magic.
2) Templars get a +15% healing bonus to all Restoration Staff healing spells, and a -15% dmg for destro staff attacks. Also change the Sorc: -15% for Resto staff.
Templars, Clerics, etc, are not tops at DPS. They shouldn't be, trading healing for damage. But they wear heavy armor, and can sometimes act like tanks. Templars, Paladins, etc, are known for fighting in the front lines, healing as they fight.
3) Melee attacks by Templars give healing or buffs to allies.
To summarize, this would make the Templar the best healer, no question. Sorcs could still heal, but not as well, even with their better magicka regen. Templars can generate healing by melee fighting, but will never get close to Sorc DPS.