Only do the package if you are afraid there won't be any seats left at Fantasmic. There's only a risk of that happening peak season.
I've done the package several times for fear of a line and the unknown. I finally tried doing it without the package (and eating where ever I wanted) twice now; the end of August and last year the end of October. We entered the stadium (no line) one hour before and we had the best seats ever (center, half way back).
You are only guaranteed a seat wtih the package, not better or good seats (the package seats are off to the far right), up until 30 minutes before the show, then they can open it up to non-package guests who can't find a seat.
The waitress will give you a voucher to enter a special entrance and she will tell you to get to that entrance around 45 minutes before but no later than 30 minutes before.
A few times I did the package, I entered about 40 minutes before and sat to the far right and I could see that there were still MANY great, better seats to be had so, to make a long story short, you don't need the package off season.
My experiences with and without the package were Aug, Sept, Oct, Nov and Dec.
In October, IMHO, you do not need the package if you enter the stadium about an hour before. With the package you'd be entering between 45 minutes and 30 minutes anyway.