An effect of making it immobile. My idea is not for the sake of other skill having a damage increase because of this possible holding effect, but this additional effect allowing a better grouping of a certain amount of enemies, cause today, as soon as enemies are grouped by Dimension Compression, they start moving again.
A stun chance works here too. My idea is leaning towards an effective support, as a disruptive move, not a damage increasing skill.
This slow interaction, for me, can be removed. Unless they make it a substantial increase in damage, it will not worth the ride. And, if by any reason this interaction creates a huge gain in damage, so what was the point of moving Sage to the support role? It would be better and less problematic to keep it as a DPS class and adjust the sfr and what else would be needed to better fill the DPS role, instead of a forced interaction with Slow to deal decent damage.