Zaj, just did a quick test with Mayasura using data obtained using -debug. I allowed myself to be slapped around 28 times before casting Val's blessing then 34 times with Val's blessing. The table below shows the statistics from the data. Basically, Val's blessing had no impact on damage taken. Granted it's not a huge data set but you should be able to see a difference if blessing was giving 40% reduction. What's your take? I can send the cropped data from screen shots if you wan to view it.
Blessing of Valakas Damage Reduction
Mayasura; hard mode
Without With Stats
28 34 Number hits in data set
367 363 Average damage per hit
112 105 Standard deviation
31% 29% CV (measure if variation around mean at 1 std dev)
575 617 Max damage per hit
183 180 Min damage per hit
Pardon the poor formatting. Couldn't figure out how to use columns here.