I got the Boss mail, so ran the 5 stam event dungeon ~times, and perhaps it is a little larger, its hard to tell. It surely doesn't feel like 2x-6x. Did they mean you needed to buy the pass for the "supercharged" rewards?
If so, I think that should have been clear in the mailed announcement.
I still think the "rebalancing" of tickets/shop purchases done a few months ago where the ticket rewards were made 10% of what they had been, and shop prices doubled or tripled, was a terrible idea and removed a lot of fun from the game. Not leaving the shop items in the entire event so we could plan and work toward a goal was the second error.
I strongly recommend to DB that they reverse those decisions. Easier access to items gives a sense of accomplishment and investment in the game, and will result in many more purchases. And, I really recommend bringing back the $19.95 30Kgems/month offer for all players. You could have likely gotten $20/month from me that way. Right now you get $0.00 and I'm spending more and more time on two other mobile games, one that is completely free (and I may donate to them for a job well done) and one that specializes in microtransactions which are all purely optional.
(I'm repeating this hear because it is a main post and perhaps stands a better chance of being read by a BF employee.)