i did a skirmish with me having all the good stuff.
stood in front of a fortress and they never triggered the shield. or the armor of vengeance effect as far as i could see.
went against another archer rook and i saw my shield trigger once. could've been anything.
Now, i might have imagined it, but the sedna i fought had that "absorbed" text very often over her head ... more than I felt was possible with 1%. And the only QoT was on my side.
However, if you're in the thick of it and you fight against solo rook, you could simple get triggered by archer,tower of light,trebuchet and melee, wich will be at lest 4% per second. add 4 towers from the tower farm and we get 8%.
And once the shield triggers every arrow paints a green "absorbed" over her head... that kinda burns into your eyes.