Dragon Age Inquisition - How to kill a high dragon in 2 minutes (nightmare)

In this video I explain how to kill a high dragon in Dragon Age Inquisition in a very quick fight, using Mark of Death and focus skills. This tehnique woks even in nightmare difficulty. This dragon is the Greater Mistal, a level 17 high dragon. My party, when the combat begins, is level 18. This works at lower levels too, but having upgraded focus (lvl 3 focus skills) is extremely helpful.