"If you find an exploit or think someone is hacking the game, please send a detailed e-mail to
hacks@blizzard.com.
Thank you for your due diligence with this. Reporting these issues is incredibly important, but at the same time please remember to report them through the secure channels."
I have always had scenarios like the one described in the OP when there is an increased number of Brazilian players in the match. I have always believed it to be server sync related issues as my latency wasn't really being affected.
However, if you truly believe this player was just a bad hacker, report. (Video/screenshots are helpful!)
There have definitely been times in WoW's history that people were able to lag/crash clients, even with in-game tools/methods.
I'm not sure what exactly you are looking to get out of this thread, but without some kind of conclusive evidence you will not likely garner much support. (Video/screenshots are helpful!)
Hacking is a serious offense. Naming and shaming someone without providing evidence is wrong. (Video/screenshots are helpful!)
If you suspect something, report what you have/think to Blizz and have them investigate. (Video/screenshots are helpful!)
Opening a thread discussing whether or not anyone else has seen similar things and discussing the different possible causes of those events would have probably been more productive. (Video/screenshots are helpful, but not necessary!)