Mmm... I don't raid until sunday, and last thursday the 2set wasn't working well at all, but I just finished a flex raid and Shield Guard was responding much better, producing no overheal at all if you were previously topped off:
[18:25:15.383] Ápplejack Soothing Mist Merithra +0 (O: 0, O: 12875)
[18:25:15.526] Ápplejack Renewing Mist Merithra +0 (O: 0, O: 9525)
[18:25:15.882] Earthbreaker Haromm Froststorm Strike Merithra 54193 (A: 71303)
[18:25:16.100] Ápplejack Soothing Mist Merithra +12876 (O: 0)
[18:25:16.274] Erÿah Beacon of Light Merithra +14854 (O: 0)
[18:25:16.274] Merithra Shield Guard Merithra +21391 (O: 0)
Anyone else have been looking at recent logs? Seems fixed.
PD: Also, after getting a flex drain life trinket, and trying it on Nazgrim... I may give it a chance again in a proper raid, but I think I will finally set for stam/crit trinket from garrosh and str/crit trinket from Paragons. No dps str users on our raid group, so free way for me.