If you play the video at 0.25 speed the Holy effect seem to actually be cast by the Paladin, maybe sort of like a new Flash with damage? I don't know. I'd love for WHM to have a mini-Holy like AST's Gravity(!), but in my opinion the Holy-effect most likely is not cast by the WHM. Sadly. So it must either be a healing spell or some kind of buff.

https://youtu.be/3_JxY2pRHn4?t=316