Here's a quick video showing that I do not take damage from attacks I ran from.
What this means: if you run 'across' a monster's hitbox, then it almost always lands. In this case, use a skill to interrupt it. If you're running directly 'away' from a slow-attacking monster, then it is quite easily dodge-able.
Edit: this is why I don't think it's a particularly large problem. Running 'across' the mobs as in Rush's video is generally poor positioning and if you are unwilling to use an ability or two to interrupt the swings you should be taking a little bit of damage. If you're actually running away from monsters then it's still very possible that you won't be soaking up all those hits from half a screen away and you will be fine.