Too many 4*s

Zyrook

I've got, like, 9 4*s covered and I'm at a lost on who to go for. Bare in mind I've got 34 4*s already champed already, so I'm not exactly hurting for choices.

Vaulted 4*s:
Mr. Fantastic - I've written him off for so long I didn't notice the re-tooling and how nuts he is with Medusa and Carnage. Plus he's coming up as a PVE reward.

X-23 - I know she's good, probably the best Vaulted 4* I have un-champed. But I've had her stuck at 5/1/5 for so long that I rarely used her. Finally got her to 13 covers, but not sure if it's worth it now.

Fury - I've had him sitting at 181 w/13 covers for so long he's almost become a landmark on my roster. I feel he's overdue for a retooling, but at the same time he's not so bad that he's desperate for it.

Bucky and Falcap - Whenever I'm forced to use them I enjoy them and find them to be solid, but every time I think about champing someone I can't bring myself to put them at the head of the pack. Am I missing something about them or are they both just middle of the road?

Active 4*s:
Riri: I've got 2 covers for her on the vine and time to use them, plus I've been hearing a lot of 'Not as bad as we thoughts' going around for her these days. She's going to rotate out soonish, so is she worth it or let her pass?

Mordo & Danny Rand: Two 4*s that I've almost never used. I honestly can't tell you what either do. Am I missing something with them or are they bottom tier of the current 4* rotation? Got a Mordo cover on the vine.

Cloak and Dagger: I like what they do, but I've only used them once or twice and never fully covered. They're at 5/2/5 right now, and by the time I have the ISO to champ I'll have the CP to buy the last cover. Are they worth snubbing the rest of the already covered 4*s to get up and running now, or should I wait for the 13th cover to come naturally and champ them then?

Gamora and Grocket are top of my wishlist, but at 0/5/1 and 2/1/3 respectively I'll likely get 2 other 4*s champed before they're at 13 covers.

Ducky

From a simple supply and demand standpoint, I'd go with the Latests that are covered first. Riri, for all the flack she's given, is great when boosted. She packs one hell of a punch with her red and her green hits pretty decently while sending the opponent airborne (help avoid an incoming attack or CD going off while you set up the KO).

Iron Fist is pretty decent as well. His black is very powerful. His blue is mediocre, though, and his green is probably average as well. 

Mordo is....Mordo, I'm not a very big fan of him, but you'll likely be getting lots of his covers so the smart play is to champ him sooner rather than later...just maybe not before the other Latests, lol.

C&D is really fun, and if you get their final cover, I'd champ them before the others. I wouldn't blow the CP on them just yet unless you have a couple covers on the vine.

After those 4, I'd start champing the vaulted ones at your preference until Gamora or Grocket come up to bat at 13/13.

Hopefully this helps you a bit.

Calnexin

For the new ones, I've had Mordo and Danny champed for a few weeks, and just champed Riri today.  

I don't know about Riri yet as I haven't had a chance to use her.  I see the utility as a counter, and her nuke is solid.  I intend to start incorporating her next season.

Mordo is... ok.  He can self-accelerate, popping off small nukes almost every turn, allowing you to whittle down foes and cap it off with a decent AoE to end the match.  I tried a few combinations to see if he synergized well with others, but haven't had much luck when he's not boosted.

Danny works really well with C4ge, because he can convert those protect tiles into strike tiles, and add fortifications to boost C4ge.  With other strong tile generators he can be similarly useful, though the utility of the fortification is limited to merely keeping them on the board, rather than fueling a nuke.  If you have and like C4ge he's worth pursuing.

Of the older ones, Fury's never done much for me.  Falcap plays pretty well with Bl4de on both offense and defense, but the team relies heavily on the presence of red to make the most out of Falcap's strike boosting.  The high cost of his power dive means Blade will keep his frenzy going on defense unless the AI lucks into a huge multi-cascade of red.  That duo pairs very well with Medusa for the purple supplement and attack tiles to double-tap the boosted strikes.  Beyond that trio, he can work ok with other tile generators, but you'll rarely be using his nuke.  It's really expensive, and when you do get it off it's usually overkill for regular foes.  Maybe helpful for some boss battles, though, if he survives long enough.

Magic

I think Mr F opens my vaulted list since I have most of the latest champed (only Gamorra, C&D and Groot are not done but I don't have the covers yet). The Carnage/Medusa/MrF is an easy skip in sim for 4* player, even for high points so it's a good team on Defense. I will consider championing when I have a cover on the vine.

On your list X23 is a decent option as well but not essential. She can be a bit of help with the Thanos clearing teams due to true heal. Won't see much of play even when boosted (surely depends on the list for a given week). 

For the recent options - Riri is actually ok. One of the better red powers in 4* land so in PvE she can work well when boosted and you can feed the red. Nothing to write home about in PvP.

Rand was kind of fun with Blade. He basically needs a partner that can benefit from his skills. Think IF-Blade-IM40. You fire the yellow on IM40 and it's pretty much good game, thank you - if it resolves. You get the Red to turn Blade into a monster, you get the blue to add the green (that you also have ready from IM, so you will fire it twice). Quick and fun. So IF can work not boosted provided you have a special tiles on the board and need a green ap for another toon.

Mordo - i have no clue. I will try him this PvE a bit as support to Agent Venom (his 9k for 5 black plus 2 random is good. I pair him with IF and Peggy but might take Peggy out to try Mordo as black feeder). Seems like this would be his niche. Feed black and/or charged tiles. 

No opinion on C&D as I don't have them covered almost at all (less covers than Groot and Gamorra). 

iron-n-wine

As far as Riri rotating out - she will be there a while still, as she is after Gwenpool, Blade, Agent Venom, Medusa & Captain Marvel

Warbringa

Can't wait for Agent Venom to rotate out.  Calnexin's post is accurate and I would listen to his advice, other than Fury part.  I always like Fury, he isn't great but I think he isn't as bad as the forums make him out to be.  His trap ability is still the best trap power out there and can be devastating, killer when boosted.  The nice part is that you usually don't see too many blue powers with mega damage (Iceman has one, can't think of other 4*).  His purple is ok, but countdown dependent.  That used to be bad but with so many of the newer characters having a similar mechanic, I don't think it is as big of a drawback as it used to be.  His yellow is his worst power imo.  It does a little of everything but nothing great and you need to have other AP to fire it at max efficiency.  There are far better yellow powers out there for 12 AP (but at least it doesn't use the other AP colors).  His health isn't great.  Maybe I give him too much credit lol.