First I would wait to see if they roll out the zader bug fix and see where that went. It "should" be this week.
If it's not to crazy, then he's over all more useful as he can add to raid scores, which leads to better gear, which leads to better arena team and more options. Don't worry about tarkin, tfp is a must and you should look into a fast boba or shore, you will need the protection for palp.
Qgj is totally viable in arena, especially if yoda is there to get a quick tenacity up.
No anakin is your biggest issue with qgj, ashoka and aayla would be my go to placeholders until he was ready so there's that issue too. Don't waste anything more on JC or lumi ( at least until zumi is released )
Good luck