I agree on the spells. The way they did it was really strange to me...It is still very confusing for beginners who will just think Fire 2 is a better Fire 1. Your solution sounds nice.

On the roulettes, I personally think they should change the dungeon roulette and split it in two at the very least.
Lvl 50/60 dungeons
Lvl 70/80 dungeons

The likelihood of getting level 80 dungeons in the roulettes would be extremely low otherwise, due to the very large amount of level 50/60 dungeons and the low amount of level 80 dungeons, but also due to the fact that people would need to be 80 or higher to join...