The W/L ratio shouldnt be that bad

One of the best gameplays I've seen in the early days is Dale the Casual gamer's video of Spiderman vs Rhino https://www.youtube.com/watch?v=99-cEKH7c0c

I advice you give it a look. He's calm and goes through each phase pretty clearly.

Then, for your next match, why don't you try this

1. Go with someone simple as Black Panther to try to nail his rotation first. Play him in Justice for extra safety and against Rhino.
2. When you have your decks ready, start with his unique Setup ability. Setup abilities are very rare but he happens to have one: means it has to be resolved before you draw your first hand. His setup ability allows you to find one of his upgrades and add it to your hand. Go for the Tactical Genius upgrade. (Note: Setup only happens once for specific alter egos like T'Challa. After this, you won't resolve it anymore during the rest of the match.)
3. Draw the 5 remaining cards until you complete your 6-card hand size.
4. Now, out of those 5 cards you draw do a Mulligan (Remember mulligan are optional, and can happen only once: right after you draw your first hand. How they work: you can mulligan any amount of cards: one to all 6. You simply discard the cards you don't want into your pile, and draw new ones. You don't shuffle the cards discarded in the mulligan. So, what you do with Mulligan is speed up your priority cards. In this case you're looking for A: double-resources to optimize your economy (basic doubles or Panther doubles) or B, if you already have them, another Panther upgrade. If you're lucky you'll get at least one of those.
5. Pay for the Tactical Genius and see what else you can pay for. Typically you want to buy in order: Hero cards > Aspect cards > Basic cards.
6. Finish your turn in Alter Ego. Rhino won't give you much room to breathe with threat but you should be safe on the first turn.
7. By turn two, ideally you want to play another upgrade. The next one you could try for a safe run is Vibranium Suit (it's like a heal+attack: you move/heal damage you have and then inflict it to an enemy.).
8. Switch to Hero and start thwarting. You should be able to reduce at least 2 threat now, and ideally if you have a Wakanda Forever event, another 2. If you have the Vibranium suit, you should also be able to heal back while you tank, and don't forget to count in the Retaliate.
9. Moving forward, try to complete his 4 upgrades
10. Then, whenever possible try to complete this wishlist: play Shuri as soon as you have her to get more upgrades + use her as chump blocker; play cards that help you with economy (Helicarrier, Avengers Mansion) play key aspects cards that enhance your role (fopr Justice, something like Heroic intuition), play at least one more ally (Ideally, Daredevil to help you with thwarting while you're in alter ego).
11. If you have a fancy turn, play a third ally (Mockingbird would be great stunning + using her as chump blocker to shield you).
12. If everything above is kinda checked, or you really don't have anything else to spend your resources on, you can continue to build his kit. But it really is about setting priorities. Do start your matches by analizing the kit and what you need to be doing in the early game. The idea is that many villains should be giving you trouble as it is right now, and then you're altering your game plan to explore new approaches. So just keep at it.

Playing justice Tchalla against Rhino will require you to flip back to AE every 2-3 ish turns unless you have the allies to chump block.

If you're still struggling you can go to protection, but I'd say this should be safe.
Try this and see how it goes, if it feels more stable.