They don't have a random drop sequence now. Its still the same every time, but its harder to keep track with so many drops.
I believe ToT has been modified 4 times:
The original: The elevator slowly rose up to the top, the outside doors would open, you would slip, and then drop, as MrP explained. This wasn't the most thrilling, but definately the most dramatic sequence as they really built up your anticipation of the drop. The tension was like that of RnRc's launch. This configuration also fit the ride's theme the most as it was the most realistic. Seeing the elevator doors open from the outside used to have a much greater effect, because they didn't open and close every couple of seconds. Instead, each one would open every couple of minutes revealing an elevator sitting there, waiting to drop. Don't get me wrong, the newest configuration is really fun, but they went a little overboard and ruined some of the ride's effect.
2nd configuration: Before rising up to the final drop, you would do a half drop unexpectedly, followed another teaser drop, a rise up to the very top, another teaser drop, and the final drop.
3rd configuration: It was the same as the 2nd configuration, but at the end, the elevator would rocket back up to the top and drop again without stopping. *This was my favorite configuration*
4th configuration: A few drops were added, but almost all of them were full drops.
5th configuration: The current configuration.