Why mark targets?

[Bridgeburner]

what i meant to show on the second picture was the enmity indicator, the bubbles before the HP bar of the mobs.

You can see the limits to the utility in this picture, too, though.

A solid red orb means you have threat, but by the time that orb changes to a red triangle, you're typically already losing the monster's focus.

Additionally, as demonstrated in this picture, you only get those floating health/threat indicators on enemies you've attacked. This picture shows the Princess and two Soldiers, but the threat/health indicators are only showing two of the three targets. (The person taking the photo has not interacted with/done damage to/established threat on the 3rd target, thus no indicator.)

... out of curiosity, why's the DPS fighting Soldiers in Cutter's Cry? Usually Heals secure aggro and sprint 'round the outside to let everybody focus the Princess down, no?