If they're refusing to follow a stance order in any mode it sounds like new bug. Your other ticket should sort that out if that's the case.
As far as movement speed. The AI shouldn't cheat, but only 'know' an enemy is near if they 'see' them. Given that's the case I would hope they would move more carefully, and slowly, in stealth mode. There's nothing stopping you from setting them to "aware" if you want them to move normally, or set more waypoints in the editor.
With combat mode I don't care what they do, as everything is so random that it usually doesn't matter how hard the AI tries to be careful in a firefight. In fact it seems to me like combat mode does more harm than good a lot (if not most) of the time. Which is what this ticket is trying to solve.