@Ziimz you took great effort to rule out your system as a cause. But this is clearly caused by the new patch 8.3. Some nice reads…
- AH Issues (still not solved) Auction house+mails - #26 by Sapfiron-razorgore
- MAC Client Issues (I cant play anything remotely close to BfA) Mac issues - CRASHING, LAGGING AND STUTTERING AFTER 8.3 - #82 by Gruthless-moonglade
- Many quest bugs/items or completions not rewarded
- etc. etc.