Wow, lots of responses since I was on including the usual apologist viewpoints. I will try to answer as many as I can.
I went in early May. The tour guides definitely went into the party with the group and the tour group did for the most part stay together. The tour guides on that evening mingled with and entertained tour group attendees utilizing most of the main room for the majority of the entire event. When it was time to line up to go out to the show the tour guides called their group together at the front of the line and they were first behind the storm troopers.
I do want to make something crystal clear. I have been to this party twice before without the tour group being there. It wasn't my "feelings" that got hurt. It wasn't "my attitude" about what was happening. There was a quantatative difference for me in the parties. I had been to a great Dining With An Imagineer lunch earlier that day with a terrific Imagineer. I was in the early part of my vacation and I was in a great mood even before all the cocktails. I didn't fly off the handle or have instant envy that someone had a more exclusive "package" than me. There are measurable differences in the experiences if you have reasonable expectations based on prior experiences of this or other dessert party events and the advertising. While they may have fulfilled a literal reading of the promotion material there also is a term in the law about implied benefits and common practices. I could go on and on about that. There can be differences one would not reasonably expect such as if your big thing was to get there early enough to have a table not far from the food and drink. Maybe it was to be right behind the Storm Troopers as you are led out. Neither of those would have been possible on the night I attended.
My viewpoint comes from this background...I work hard for my vacation money, it's not a gift. I don't get an employee or friend discount, comp. tickets, blogger discount or any other discount for this type of event. I'm not local or a CM. I am a DVC member with a higher than the average number of points and an Annual Passholder (but you will never hear me say those to expect more or specialized treatment). I am not a chronic complainer nor a whiner. Most things roll off my back and in fact one of my jobs is to be the go to level headed guy to sort out the disputes fairly. I sat on this a week before contacting guest services to be absolutely sure there was no emotion, anger, envy or pettiness involved. I felt strongly the policy should be changed or at least guests should be advised ahead of time. If it doesn't effect your experience as some have tried to say, then what's the big deal about changing it?
From a logical monetary aspect the Tour cost is $121.12 for a 7 hour tour including guides, 2 reserved show viewings, lunch amongst other offerings and the Dessert Party is $69. a $52 dollar difference. So why does the Tour need 15 additional minutes of the party, priority access and space?