I'll give you my experience but don't take it as gospel.

I applied round 2 last year and, come decision time, was waitlisted without an interview on March 17. I flew out to interview as soon as I could and was dinged on May 11 (a few days after round 3 decisions were released) even after taking my GMAT a third time and improving 20 points and getting more recos. When I was there interviewing in April, there didn't seem to be many people in the application process. Things seemed to be winding down. I'd be willing to bet a lot of money that had I applied round 3, I would have just been flat out dinged.

I don't want to say you shouldn't apply round 3, but if you can put together a very good application for round 2, I'd highly recommend it. Especially because the class size is so small.

Good luck out there! I loved the school, the people and staff were all really great, and it'd be a fantastic place to spend a few years.

My understanding is that R3 for Haas is different from other schools' R3s since they have 4 rounds, so you have a better shot than in R3 for other schools. However, keep in mind that even though the R2 deadline is early (December), they give admission decisions at about the same time as other schools do for R2 (mid-March). The R3 notification isn't until April 21, so you will be further stretching out the admissions timeline. I'd definitely go for R2 if you can complete an application you're happy with in time. If not, wait until R3.