This is the first and only time I've ever seen this (even on the bard I had), so might be a one-off - but while you're in there focusing on non-sliding enemies, might wanna take a browse through Otto's dance.
Was in demonweb yesterday with Double Rainbow active.
Shot one of the demonic spiders and Otto's Irresistible Dance proc'ed.
The spider continued to move toward my character, STILL DANCING (which was actually funny as hell) and with the icon still on his head. He could still melee.
Now 1) I thought they were immune to mind effects like that? 2) shouldn't he have just stood still upon proc? and 3) he shouldn't have been able to attack when I was within melee range.