Having just done the maths the fact that you need 5 7* Jedi isn't as bad as it might seem.
Granted I already have a few decently starred, but I am entirely missing 1 jedi, as the others I have are pack only, and I don't want to shell out cash for this.
The breakdown is basically if you start from scratch and refresh Cantina once per day, farming Lumi, QGJ, Plo, Eith Koth and JC, you can just about hit 5* on all of them if you start farming tomorrow and put everything else on hold. Assuming a 2 week gap between the end of this one and the start of the coming one, and again assuming you only farm these characters, you CAN get them all to 7* in time.
So if you want a 7* whoever the character ends up being, start farming now. When the event hits, we'll know whether you want the character. Worst case you lost 1 weeks worth of farming other chars, not the end of the world, but best case it's Yoda and one month from now you're sitting pretty with a 7* Yoda! :)
EA Staff (Retired)
