Perhaps they should turn execution sentence into a meteor: explodes on single target doing x dmg, spreads it to all enemies near target up to y dmg.
Having seen the variety of champions blizzard has made for heroes of the storm and overwatch, they need to recruit some of the designers on those teams to fix ret. I understand they are overall very different games, but there are enough rpg elements in both of them in which I think the challenge of making a limited but distinct class toolkit (the goal of legion for all classes) would be exactly what they could bring to the table.