If you're running dungeons at a regular pace, chances are the healer don't have time for that between pulls. I'd only take time reapplying with a particularly slow-moving party [excluding the tank who'll always get it before he runs]
I pretty much never bother unless Swiftcast or Lightspeed are up to Stoneskin on the move before the next pull.
I completely removed it in favor of Blizzard 2 on SCH a while ago and have never felt like something was missing.
Stoneskin is nice to have but you have to ponder its opportunity cost or lack thereof.
