Utility flask should be able to remove marks.

Blight is a bit different. During play, arpg servers only update actors within a certain range of player(s) on a map, for obvious performance reasons. Outside that radius, no AI "life" is happening, so for example shooting cones of arrows far offscreen with a heavy projectile speed buff is a successful cheesy tactic.

In blighted maps, they violated this rule, boosting monster update radius to whole map, so mobs would never stop moving (that's why those maps are empty - too much server load otherwise), yet towers are still only updated around the player, which makes all those faraway tower spots a joke - player can only build at the center of map if solo. And the game never bothers to explain this to common player, as usual.

Point is, I am pretty sure Deadeye mobs cannot mark you from outside monster update radius, so it is certainly not 2+ screen range. But with no visual hint to mark origin, even 1.5 screen range is too much and needs reduction.