I used to "track" the CLASS ADVANCEMENT events in excel sheet over a few months, the conclusions are:-
1) they came in random orders
2) some classes may not show up in an entire week
3) some classes may appear twice in an entire week
4) there's no specific sequence
5) there's no clear pattern
6) it can overlap with LEVEL UP even or not, again, purely random
7) best case I saw so far is 2 adv overlap with 1 Level-up, worse case 0 overlapping, normally on average 1 overlapping (haven't seen any with 3 overlapping, or not that I can remember)
Comments
All the solo events are random. The one you want will normally pop up fairly soon
1) they came in random orders
2) some classes may not show up in an entire week
3) some classes may appear twice in an entire week
4) there's no specific sequence
5) there's no clear pattern
6) it can overlap with LEVEL UP even or not, again, purely random
7) best case I saw so far is 2 adv overlap with 1 Level-up, worse case 0 overlapping, normally on average 1 overlapping (haven't seen any with 3 overlapping, or not that I can remember)