This is more prelevant in maps with an incline like the Solarium Ascent where the interaction happens on a sloped elevation. Obviously it is only noticed when interacting with a mob with a ground based AoE…
In most cases the Aoe animaion is sliced by the ground… i.e. the aoe is flat, but the ground elevation is angled so the aoe disappears in the ground so you tend to see half of it, instead of the aoe following the contour of the ground correctly.
In some cases, the Aoe disappears entirely but is actually still active, and can be seen by moving the char around the area - the aoe briefly appears depending on the angle.
A similar anomoly like this appears in the Arena maps where there is the elevation around the central Arena, occassionally AoE effects are spawned on the elevation and either are strangely vertical without any link to the ground or are cut in half/only partially visible due to the clipping through the ground.
Very difficult to take screen shots of this, but its fairly easy to replicate provided mobs that have ground Aoe spawn.