Bryn is great on offense, she is ok on defense but if you’ve got maxed 5* they should likely be the priority long-term.
There is not one correct answer for defense, it’s about working with what you’ve got and remember offense is more important than defense.
Some notes on your heros.
Vivica - she is an decent tank (costume is better), an ok flank and a terrible wing. As tank with emblems like you have she is decent, problem is purple is stacked with options for attack atm.
She is still probably your best tank for now.
Thorne - is an ok hitter, but meh though due to now secondary, don’t take him past +7 for now, unless nothing better comes along. Interesting to see what his costume offers if released.
Sartana & Kingston are great, lock those two in… although Sartana counts Anzogh out due to being the same class.
Neith & Joon - Neith is underratted utility / flank on defense, however Joon is alround solid, so probably him next. Ranvir isn’t much good on defense due to low health, titan specialist.
Marj / Azlar / Elena - Marj is the only real red sniper and worth maxing next, also you don’t have another 5* rogue that I can see.
Long term i’d look to something like:
Sartana - Joon / Neith - Kingston - Thorne (until he can be upgraded) - Marjana
Sartana - Throne - Vivica - Kingston - Marjana
I personally would be tempted to double green with Kad & Kingston over Thorne, but alot of people advocate rainbow… if you are doing this, have one at flank, the other opposite wing, or both wings.
I’d take Kadilen to +7, if that means stripping Brienne, so be it. Try and keep the other two 4 with emblems as I assume you use them quite alot.