Visuals
I think it would be nice if the ‘Mark for Death’ spell had a stronger delineation/indication on cast (as to the area affected) as well as displaying which MOBs are affected. Perhaps an actual outline on the ground at the time of casting that slowly fades. The concentric circles at cast time do not, imo, really reflect the extents to which the spell effect occurs. Also, the pale green icon of affected MOBs is, to me, quite easy to see/lose sight of when fighting clusters, small or large.
Nodes
The ‘Long Gaze’ (area of effect increase) does not seem to greatly impact the actual area of effect. Perhaps tweaking the visuals would just make it easier to appreciate the base radius vs. the improved radius (via this node)
I think a node that allowed the spell to become an persistent aura would be nice, especially for melee-centric builds. It could have a diminishing effect on other aspects of the skill, but would allow it to be in effect at all times for close combat.