I didn't find any information but I just logged on (during work hours :S) and did some quick research where i held my mind static and varied my determination, only two sets, with determination lowered by 27 points.
The set with the higher determination healed for 774-821 and the set with lower determination healed for 758-804. This was done on the same AFK player in Ul'dah.

So I was wrong. I'll need to respec MND > Crit > Det instead. Didn't even have Determination as a variable for my gear before.