Well, after looking up abit on Dementation, here's a few good ideas for a replacement for Insight.
"Voice of Madness: Provoke extreme fear or anger in target."
This power of Dementation could either could work like Serpentis 4: Phobia in the FN mod (Except instead of crouching down in fear, more like hysterically running away) and/or like Berzerk, without the death and only able to use fists. Depending on how you guys want it, it could be area of effect or single target, and the "anger" part could happen less often than the hysterical running away (thinks back to Simon in the Abandoned Hospital in VTMB).
"Shattered Mirror: Twist a victim's personality into a copy of yours."
I kind of imagine this working like either like Mask of a Thousand Faces of Obfuscate, where everybody starts attacking the target, or like the Target starts attacking everybody until everyone else dies.
"Confusion: Cause the target to wander around in a daze."
Well, its like the Forgetful Mind of Dominate, but this version would cause the target in question to not notice you until it wears off. Could be area of effect or Target discipline. And would greatly help in Feeding.