Originally Posted by
Bigslick
Limiting shield casting by a max # per time period would just be a bad idea, somewhat defeating the point of soul warding. If this becomes an issue Blizzard wants to address and make a less attractive option, a more reasonable solution would be to apply a debuff similar to that applied to mages upon casting arcane blast, where PW:S has a base cost but applied a 4 second debuff which stacks 4 times that increases the mana cost of additional PW:S casts while active (but without the extra throughput provided by AB -- though that could be an interesting mechanic too). Chaining 2-3 shields wouldn't destroy your mana in such a system, but attempting to spam it WotLK style would be infeasible even with a wealth of innervates and MTTs.