Just some thoughts:
Strong candidates:
Kamala Khan 4/3/5
There’s color competition with her Green & Purple. However, her Purple could get you to both high costing Green hit-all attacks much faster, and provide cascade generation (which you do already have with Thor’s yellow and sort of Doom’s Blue though). The fact she’d be level 153 is pretty strong too.
Daken 3/4/4
True Healing along makes this a worthy choice. He’s great at grinding through PVE nodes. Ideally you want 5 5 3 or maybe even 5 4 4. Since he only has one active skill, and it’s in a color your team is weak in, you won’t have to worry about color competition. The only problem is he might be too low level to tank his colors for you to save Doom from damage. It depends on what his max level is compared to Doom. I think they work well together because of that. My Doom tends to die a lot because I make too many matches with his colors without someone else tanking some or all of his colors (pretty hard to have someone tank his Black, and they are all equally squishy)
Luke Cage 3/4/4
Even though he’d soft cap at like 140, that 4 in Red is a MONSTER for grinding in both PVP and PVE. I used my 5 4 3 in the Ultron event, and he pretty much negated all the strike tile damage from the Ultron Sentries. Yes, eventually you want 5 Yellow, and either a 5 5 3 or a 5 4 4 build (I’m kind of partial to 5 4 4 cause the 4th Black adds a 1 turn stun if his Countdown tile is out). The only problem is that he doesn’t provide skill is colors you don’t’ already have. You’d never use his Black with Doom. Also, even though at 3 Yellow it still packs a big punch (pun intended), you probably wouldn’t use it much along Thor (and Thor’s is even a cheaper skill by 1 AP!).
Mystique 4/3/5
She’d compete on all of Doom’s colors, but remember how irritating the two of them were together in the Rocket & Groot PVE? Granted, you wouldn’t have a goon feeding them all three of their colors every turn, but they still work well together. It would give you a Blue that would give you both of those colors and a cascade. It would also potentially give you some AP steal and a bit of stun with her Purple (and AP drain with Masterstroke). At Level 153, she’d pack deal big time damage with Masterstroke if you ever need a big single-target damage skill instead of Doom Demons, like as a finishing move.
Interesting choices:
Daredevil 2/4/5
The 5 in red is great, as is the 4 in Blue, which would give you a stun. The problem is your Thor yellow might blow away both of his special tiles. he would lurk in the background though because he’d never tank any of his colors, meaning he’d be tough to get rid of.
Iron Fist 2/3/4
A bit under-covered, but his Purple is one of the best skills in the game, and could speed rush your way to Doom’s Black. The free Attack Tile every turn is helpful for sure.
Magneto 3/2/4
This would be a prime choice because he has very strong skills in the two colors you aren’t covering, Red & Blue, but he’s a few covers short in them.
Ignore for now:
Squirrel Girl 5/4/3
Could be fairly high level, but un-optimal covers for sure. 3 5 5 is what you need, and since you would never use her yellow while using Thor (or her green for that matter), not a good choice.
Captain America 4/3/4
5 Red AND 5 Blue is a must for him. Being able to target countdown tiles is huge (and 5 in red gives a massive damage increase).
Punisher 4/4/3
A really decent character, but with Thor you’ve already got good Green & Red with Thor. And Punisher’s other skill you’ve already got covered with Doom’s Black, and it kind of does the same thing (Attack tiles for days).
Patch 2/4/2
Like Daken, his True Healing is wonderful for grinding PVP & PVE. I use him almost exclusively because of that alone. However, if he doesn’t to tank his colors the True Healing won’t help you that much. With his level cap, he probably wouldn’t even tank Green over Thor. You need another cover or two (especially in Yellow for more reliable healing) for him to truly be usable.
Cyclops 3 1 3
Even though he’s great wait it out a bit mroe. Covers will come eventually, and I’ll bet his covers will be rewarded this season’s PVP.They like featuring relatively newly released characters.
Ignore long term:
GSBW 3/5/2
You don’t have 5 in Green, and even so she’s still a low tier character even with the health increases.
Gamora 3/5/3
She’d mid to low tier. The problem is her Black is basically worthless when she’s under-leveled compared to the rest of her team or being used with other characters that share her colors, because she’ll never have enough tiles with her symbol to generate any strike tiles. She doesn’t have enough HP to be able to tank all her colors either to really make it work. However, your Thor would have match priority for Red, which would be helpful.
Spider Man 3/2/3
Ignore. Low tier character, probably one of the worst 3 stars in the game actually. Sadly his Purple is almost his best skill now. My how times have changed since he was first released…
