I was going to suggest this feature, which occurs in MMO, but then i think i noticed them in the trailer above the players. If what I see is a health bar then I think that is good, as you can not only choose to pick out the weaker enemy or heal the weaker teammate, but you get to see how much hp the enemy had before they kill you.
My only concern is that in the trailer the Health Bars (if it is them) do not seem very visible, perhaps a suggestion would be to make them bolder to stand out more.