Couple things I've seen
 

Some times when im casting, and am getting pushback from being hit, the player cast bar will disappear, though I am still casting. Sometimes this mess you up because i think the cast has been completely interrupted.

Another thing is sometimes the OOR is on over my target when they are clearly in range for all attacks.

These are not big things just thought I would let you know

I also am having both of these issues (yes I saw that the casting bar disappearing is being worked on lol).

The cast bar issue is a known bug, I'll look into the OOR issue.

If you could find a sequence of steps that reliably causes the OOR problem to occur, it would be most helpful in aiding me in tracking it down... especially if it can be repeated playing solo. (you think it's hard to get a group for an instance, try getting one to help you debug code -- lol)