The event is generally very nice! The prices are good and special. The 2 new sets are different from each other, but very desirable!
The only thing is that everything depends so much on random! You may have a couple of set collections, but one specific building may be missing and it ruins everything, the set would not work without it
. I personally would have a few optional suggestions:
1. Allow purchase of the specific building with diamonds.
2. Do not "abandon" the two sets, make the buildings available in some future events, so that players can "catch up" and find the missing part later.
3. Very controversial: implement some kind of an "exchange market", where people could have exchanged their set buildings with each other.
It would be really nice if the developers consider something from the above-mentioned!