SCH and WHM work very well together. One thing that SCH apart is the fact that we can pre shield. Casting Succor at different points throughout a fight in order to mitigate some AoE damage is very useful. I will even cast it if everyone is full and before a pull. My Succor hits for about 400 give or take and 600 crits, that is a pretty big shield. I think the best setup by far is one of each. 2 SCH do not work great together but it is very doable.