Wind Dancer + Glancing Hits bug

If using wind dancer with glancing hits passive tree node (and/or neighbouring small node of the same type) any hit, blocked or not, will cause wind dancer's explosion, and as such stacks reset. Probably has something to do with Glancing hits still doing damage to the character even though the hit has been blocked.

It doesn't sound like a bug. As you said, taking damage from blocked hits satisfies the "being hit by an enemy" condition.