What kind of information exactly would a TPK give you to prepare for running the game at this convention?
That I made it too powerful for the group, of course.
Silly DM, you are playing with 5+ min maxers, we will look EVERY option through in unison.
Which is exactly why I chose to do the campaign here. I've got no real problem with you guys beating it, and advancing it a little, but I've got issues with killing you guys off because it means I'm either incredibly mean and just looking for a TPK (which anyone can do, really) or I've made it way too powerful.
See, the other playtesting group weren't minmaxers. Not by any means. Heck, they didn't even know that it was possible for characters to be level 20 and still be able to game an actual scenario. Even if one of them did technically cheat, it was obvious that what I put them up against wasn't nearly powerful enough.
You guys on the other hand, look like you'll be able to take it. I'll admit that I was wrong in writing you guys off so soon with Blasphemy and the negative energy breath weapon. That was my fault. However, there's still a long ways to go yet.