I spent my first night with T10's 4 piece set bonus last night, and I think it was a little bit of a disappointment. The hot accounted for about 3% of my effective healing for the night, which is way less than in some of the parses I'd seen. I think that it's possible that the fights I happened to be healing for last night were generally not chain heal friendly, and I was also mostly tank healing as the other healer was a druid.
I will be more excited to see my stats from tomorrow, when we will be doing Blood Queen, the fight that was built expressly for Chain Heal spam.
Still, I think I probably will be building 2 sets, one for Chain Heal centric fights, and one for Tank healing fights. I have generally resisted building multiple healing sets in the past, due to bag space, and general laziness, but I think the set bonuses and relic effects have become so specific these days that it may still be necessary.