It has, but no worries.
Unfortunately the Merciless Hand only works with attack rolls that deal direct damage. But that includes "pulsing" stuff like Chillfog, Wicked Briars, Sacred Immolation...
It does not work with any Damage over Time (DoT) effects. Dragon Thrashed is such a DoT ability. Others would be Come Soft Winds, Disintegrate, Shining Beacon and so on. Crits with those effects get +50% duration - and that's where the higher damage comes from then: more ticks. The damage of the ticks does not get altered by crits. Hence the +0.3 from Merciless Hand doesn't get applied.
tl; dr: nope.
Edited by Boeroer, 30 October 2018 - 10:34 AM.