Veins of Malice passive with Last Laugh?

I have Veins of Malice from the Necromancer tree, supposed to be the uber final node. Gives 20% minion damage for up to 5 seconds, 10 second cooldown.

But I noticed something. When I have the passive Last Laugh from Transplant, 60% minion damage for 4 seconds, they share a cooldown! I can’t get Last Laugh’s 60% buff while Veins of Malice buff is active.

Is Veins of Malice just worse, then? 1 second for 40% less damage hardly sounds worth it.