Set Bonuses Healing Done/Healing Taken not scaling for critical healing?

ControlzU

I was testing healing buffs and scaling in the game and ran across what seems to be a bug. When I slotted a 1 piece symphony of blades shoulder piece to get 4% healing done the raw heal did increase by 4% however the critical heal was not scaled correctly. For example if my raw heal is 1000 and I add 4% healing done my raw heal is now 1040 with a 1560 critical heal, however that is not the case when you add healing done on a set piece. It raw heals for 1040 but the critical heal scales off the 1000 base raw heal without acknowledging the 4% healing done on the set making my critical heal 1540. This was also tested with a 2 piece Hand of Mephala and yielded the same results. Is the logic behind this that sets can't crit? Because when I add healing done from my champion points or the argonian passive I get healing done to crit and work the first way I mentioned. I do recall awhile back when the devs fixed proc sets in the game do to balancing issues, is this the reasoning behind this? I tested this also with healing received and healing received seemed to work but that could be because I got healing received from the skill 'mystic guard'. I have not tested this on a set like Sanctuary where its a unique healing received buff unlike minor/major vitality. This just feels odd since I add the same buff with a racial passive , Blessed champion points allocated, and the Ritual mundus stone which all seem to scale for the critical heal but my set bonuses don't do that.