Most critical is having a tester with a global perspective. That is to say one that can see issues from many sides (preferrably before they arise). Those players are few and far between. Most tickets that WIS receives, as well as forum threads that are started, have to do with how someone was wronged. Rarely will a player bring attention to an issue where he/she is receiving an advantage or bring up an issue that may not have even happened yet, but that has the potential to occur.
What they are looking for, I'd hope, is someone who is non self-serving, who understands the game inside and out and who wants to make the game as best it can be. The object is not to win. It's to try and exploit things that have been viewed as glitches in the past and then report bugs and inconsistencies. It's to head off the deluge of tickets and/or concerns once it goes live. It's to be proactive in foreseeing issues, not reactive.
As far as the testing goes, in the past they've run each "HD cycle" every 10-15 minutes, where 24 hours of HD is completed in 1-2 " testing" hours.
**Each tester should have a 1) minimum of 71,797 posts or 2) a minimum of 15 national titles and/or a run of 5 consecutive titles and 8 titles over a 9 season span.