I don't see any imprtant character left out except Dabura, Pikkon and Ultimate Gohan, I can't think of any other. But I would want Turles and Cooler. ( I don't think think they count as being importan since they're only from the movies.)
Stars aren't that hard to get, I unlocked Broly after 30 minutes when I started playing. I'm trying to get more stars for other levels, SSJ3 Vegeta can wait.
Kid Buu is pretty fast with an awesome moveset, but yeah Burter is better, but I prefer Kid Buu's moveset. (Not counting ultimates.) I never tried SSJ2 Goku, only SSJ and normal one. Maybe I did but I can't remember.... =/ And I don't like spamming anyways. (And my brother always spam. D: )
My favorite character to use for easy ending would be Yamcha, Spirit Ball + Wolf Fang Fist = epic. His melee attacks are awesome too.
I actually did a team battle against my brother today, I used the Ginyu force and he used Kid Buu, Vegito, Gogeta, Vegeta (scouter) and Bardock.
I got Kid Buu with Guldo, and Vegeta (Scouter) with Jeice. I got the rest with Burter (Vegito, Gogeta and Bardock), and Burter was in low health because of being spammed.