I like the idea of Sheath of Light. But the way it has been implemented has contributed to some weirdness with paladin scaling. The purpose of Sheath of Light was to let heals cast by a Ret paladin scale in a small way, rather than remaining extremely weak all the time.
However, there are 3 types of paladin abilities:
- Abilities that scale with Attack Power only. These are mostly offensive abilities that belong to Protection and Retribution.
- Abilities that scale with Attack Power and Spell Power. These are baseline abilities that all specs use, such as Judgement and Consecration.
- Abilities that scale with Spell Power only. Heals, and Holy Shock.
The interaction of Sheath of Light and category 2 in particular is problematic. I remember that during the Wrath Beta, Seal of Righteousness was often the best Seal for Ret. Eventually it got nerfed down, but became very weak for Holy, and had to be buffed with a deep Holy talent. The reason this happened is because if the SP coefficient was high, Sheath would allow Ret paladins to use a lot of that SP coefficient, and the ability would outstrip Category 1 abilities. Balancing paladin numbers would have been a lot cleaner if Sheath did not affect abilities in Category 2. That way you could balance the AP coefficient around Retribution/Protection paladins, and separately balance the SP coefficient around Holy Paladins.
Even in Category 3, Sheath doesn't affect all abilities. Most notably, Sacred Shield doesn't scale with the granted Spell Power. This may have been an oversight at first, but now is maintained for PvP balance reasons.
When you get right down to it, Sheath of Light as it exists right now is overly broad. We don't really want to give Ret lots of Spell Power for general use. Most of the abilities Retribution uses scale primarily with AP, and adding extra SP scaling just complicates things. But we do want to give a Retribution paladin the option of increasing the power of her heals.
Sheath of Light should become a lot narrower in scope. The SP granted should explicitly apply to Holy Light and Flash of Light only. Then the coefficients of all the Category 2 abilities should be retuned so that each spec has an appropriate result. (The same idea would apply to Touched by the Light in Protection.) I think this would make paladin scaling cleaner and simpler. AP and SP scaling would no longer depend on each other, but would remain completely separate.
Of course, this would drastically change the value of Sheath of Light. It might come to be considered a PvP-only seal. But untangling AP and SP from each other would be an overall benefit for the paladin class.