5
Had this staff since level 52. I'm at level 65 now and I have yet to replace it. A few have come close, but the +43% damage to stunned enemies as a lightning sorc is really quite incredible. I've upgraded it three (out of 5) times now -- Even Unique Sacred items haven't come close.
Was this just a super lucky drop?
Had a similar thing on my werebear. Just amazing stats, tons of near max overpower buff and major basic damage buff to the point mual actually does damage and is fun to spam. 20+ levels and still yet to replace it. Some drops are just hella good I guess lol