Team building questions

I'm a mid tier free player and ive been grinding my ass off to earn what i have. Now i have a few questions about what i should crystal and pe or pope.
I have
x2 big rig
x8 Lockdown
x8 Spitfire jaw crusher
x8 Diana Battle Maiden
x4 shellstingers
x1 F-9 mark 3 fully crystallized trying to build a pope
x1 ultra mutant pe

I have some others in my squads but those are the important ones i need help with prioritizing. I'm just not sure what to do with the recent nerfs and changes.
I'm trying to be well rounded as a free to play player i cant really have the best of the best for all events but im still able to do some solid work, so any advice would be extremely helpful thx

Big Rig - No
Lockdown - Maybe
Spitfire - No
Diana - Yes
Shellstinger - Yes
F-9 MARK - Definately
Ultra Mutant - Depending on how much crystals / res you got.

Big Rig doesn't do any damage anymore, since both his skills are nerfed so badly, and he only has 7k AGI.
Lockdown is one of the fastest mercs on the X if you POPE the AGI, good first attack merc.
Spitfire, good merc, worth nothing though. Crystals go for 10 vs. 1 AC nowadays, crystals would cost you way too much to build a nice Spitfire.
Diana, has weaken effect ( ? ) and it's a mini Cannonback, I'd say OPE 200cc.
Shellstinger, big weaken effect and a lot of damage, 200cc seems good for this merc.
F-9 MARK, definately worth 400cc.
Ultra Mutant, great merc, low value nowadays on the X since there are so many good ATK mercs out there like Incinerate.

I would say try and trade your rigs for a few primarch r1s each and put together an ope200 giga primarch. Then build an ope200 Diana and jaw crusher. On the knockdown put 40 crystals into the agility and evolve with just the 10 in the final stage to the others. Then run:

Shell-prim-diana-spitfire-f9 in the W formation. You should find the results very much so to your liking.

I also have a pe lilith reptilian she not ope because i got her when i was new to the game and didnt know about the value of crystals. Just got a v1 oathbreaker as well, will she be worth putting anything into? the squad i roll with now for every event is the M formation Cmdr Brodey left, lilith reptilian top, f9mark3 mid,uber astro v2 top, mecha horde v2 right. I have the most all round success with that formation in pvp and raid and tower. i have a v4 primark and tigrey v4 but they arent pe or ope i got them because the more i read up on thing i realized i needed buff mercs. Ill post my full deck in ahile and you can tell me what my best setup would be but im going to eat right now. I definitely want to try the formation you suggested though.

Oathbreaker isn't usefull in PvP or Tower, but might be good for new players in Raid Event. ( Makes all squadmembers attack the boss but the skill has a 20% proc chance which is, in this game, the same as 5% with their proc manipulation, lol. ) If you post your mercs, we'll help you establish a good team !

heres what i would do. buy a super cheap pope blue vulture, change to mean mary cause brody hits like a bitch, use the lilith , def finish off that f-9 as pope, and lastly the lockdown make a pope. run in W formation lockdown-blue vulture-lilith-mean mary-lockdown. should be able to pull some 30 win streaks every now and then with that. The vulture buffing your toons will make their procs one shots and those are all relatively quick mercs so you most likely will attack first assuming your not fighting another blue bot or blue vulture team. and yes blue vulture is a rare lol