AFAIK, they stack correctly in 1.10, since Blizzard has fixed 1.09's slow desync, running speed can not be lower than 1 yard/sec, though. But there is a cap of 50% in pvp.
What I am not sure is that whether slow effects of different types still stack or not now.
What I am not sure is that whether slow effects of different types still stack or not now.