Rescue does indeed need to do a bunch of work to go off.

It targets the player, confirms your position client side, goes to that player, confirms where they are, moves them on their client side, then they are moved server side - and that's when everyone else sees them move.

Rescue is one of those spells that simply don't work as well as they could because of the server ticks. It needs to go through 2 clients, and the server.