Are you sure it's not just latency? In Cathal, I tried a Hibbie stealth group (we went hunting for sasquatch and loch ness monsters) where we all had 35+15 stealth, but I kept falling behind with /stick.
I did a stealth test by dropping an item and running between it and my groundset and counting.
My impression was that it is faster about 35 base but im not completely sold on 50 stealth for speed, diff between 40 and 50 is not worth all those points imo.