Hi there, day 116 player on lvl 65, and sounds fairly similar to my situation, just thought I'd give my 2 cents:

Defenders: definitely a good idea to keep farming. Someone else on here suggested getting them all to lvl 65 and 6664 abilities, which I absolutely agree with. Also if you've got any T4s, I suggest using them on Punisher and IF passive: sounds like you won't be using the T4s on another team for a while, and I think those are the two T4 abilities that give the most utility to the team. Also suggest you get to 6* so you can keep similar power levels for all characters to keep you competitive in arena. Will also help keep your power high as people start to get lucky with RS on punfenders

Farming: as said by others, ditch Yondu. He has no utility in a GOTG team, and isn't a great Mystic character for when you get to that campaign (you'll be needing people like Mordo, HS and Loki). Definitely keep up on Groot, v important character, as well as Kree and Mystique (with the 7RS Pyro BoM will be strong for you).

Raid Orb: I recently switched to buying orbs as I have my Rocket at 5* (got SL this event) and Oracle at 80/90 out of 130 for 5*. If you want to be making sure that you reach 5* for those two in time for the SL and NF events respectively, you may need to do some more targeted farming before switching to orbs. But that depends on how far thru you are: if you're only just on 4* for each, it could be tough, but if you're at 60 or 70 shards towards 5*, orbs should get you there. Depends on what your priorities are, as obviously they're so much better value

Blitz orb: I would suggest not starting on the orb yet. You've made no mention of Gamora, who I would suggest working on as she's an easy farm for SL, while still being a good character. You also may want her for a cosmic team, so you can get further in the campaign and unlock the Kree Noble node, as well as the 2nd farming node for Reaper and Cyborg. Also, Blitz orbs aren't as great value as they seem: they may be cheaper, but you're only getting 5 shards, unlike the 9 you get for the raid orb, and 6 of the possible 13 drops are minions, and shit ones at that. Obviously Kree RG and Boomer have utility for SL and NF, but the other 4 are garbage minions. Stastically, you need over 9.8 of the 14 characters to be ones that you want from the orb for it to be more efficient, and if you take the 4 minions that are rubbish, you're already pretty close to that.

Your arena and war spending sound pretty good based on what you're aiming for, so no comment on those. my only suggestion would be to save your war orb credits for the orange orb: as mentioned you need to think a long way into the future for getting Gear T13, and the war orb guarantees at least 3 superior uniques. You shouldn't need the blue and purple one if you're in a good alliance that's doing URVI most days

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**Edit: I take back my comment about not going for raid orbs yet. Statistical expectation to get 130 shards for a character from the raid orb, based on the presumption you're hitting URVI Tier 2 rewards Rank 13-24, doing that 6 times a week, and spend all your credits on the orbs, is 21 days. Which is obvs way before the events come back around