It is tough to to talk about the high tiers of warcraft in versus, since the only times high tiers have actually suffered defeat has been when PIS and plot devices has been involved. I am of course talking about Mannoroth, Archimonde and Sargeras.
- Sargeras who pretty much can not be defeated by normal means. The only time anything has ever been proven effective against him is when an item was enchanted by the actual Goddess Elune.
- Archimonde has only been defeated by a full-scale blast from the World Tree which pretty much has the Well of Eternity flowing trough it.
- Mannoroth was a lot of PIS as well. This is excusable as Grom had drank Mannoroth's blood and Grom was using the mighty Gorehowl against him- but still a defeat trough PIS as Mannoroth underestimated Grom and gave out not even minor resistance.