Bug: Impending Doom doesn't trigger when cast from other hand

Impending Doom doesn't trigger when [assigned to] cast from other [2nd set of passives] hand.

1. Get any curse, add Impending doom and Cursed ground, lure any mob and wait.
Expected: curse expire, mob take damage from Doom blast.
Actual: works as expected.

2. As 1, set curse to II'nd set only, activate II'nd set and repeat 1.
Expected: curse expire, mob take damage from Doom blast.
Actual: works as expected.

3. As 2, cast the curse from II'nd set, bit then switch to I'st set and wait for expiration.
Expected: curse expire, mob take damage from Doom blast.
Actual: nothing happens at all.