Yes, speed and movement is the most complex thing to get right, because it impacts all things!
I still have a bit of work left on 1.5, but a little sneak peak is that staggering is added, and because of it I'll hold off on changing monster speed a lot, because it will impact movement a lot.
Due to the physics involved, a staggered enemy will also slow down any monsters behind it.
Staggered monsters won't just stop, they will also not attack, which helps a lot for melee builds.
So let us see how this impacts the balance og everything, and readjust the difficulty in 1.6 ;-)