I, as well as others reported this as soon as 2.0 went live. It's definitely a bug, but we have had no response on the issue. If you're a merc you can use HO for the root then cleanse the snare, but HO is supposed to prevent all movement imparting effects, so this issue was obviously overlooked.
I will add that if you already have HO active when the leg shot hits, it has no effect. The snare only happens when you activate HO after you're rooted.