Could swap Sonya for vela play around see what fits.
Bt as healer can be handy rather then JF just my opinion on it if you don’t want rainbow
Go tibs Sonya bt vela JF 
Don’t really have a tank I like, But you have to find a way to get Vela and Jean F in there.
That could def work. Jf would reduce the blue damage if he gets to fire. I mean I think he should if bt is there. Giving the rest of the team to kill off everyone… so it’s not always better to go rainbow?
I do wanna get vela and jf in there quickly. Their normal hits are pretty damaging in itself. But the only two tanks would be BT and rigard when I get him high enough. I have horghall but I haven’t got the tonic to finish him. Although he’s a strong tank he’s not that great according to what I have read. I was also thinking joon but I am missing the darts for him too. So JF not really a good tank either? Hopefully I’ll hit another 5* tank soon but that will take me ages to get him leveled. Think i might be missing material. Have 5 blue Tabards so hoping for a purple 
Rainbow is better as stacking is less an option.
But say Sonya bt vela people stack ice so bt flank by them ice is weak against the flanks and if a bad board can work in your favour plus JF is fast so prob will go off. if it don’t work then try somthang else 