None of them are crazy crazy hard, but HQT is the hardest. It is also by far the best so that's up to you if it's work it. Hunter is the most fun but not amazing, Warrior is okay, about as good or a little less good than Hunter.
You must play HQT. If you can't do plasma caster cancel you can just cancel all string into low plasma to stay safe and get some damage from the mixups. HQT also has consistent and optimized corner combos
Given the dirt that all the other characters that people consider "Viable" in this game have. Warrior is on the outside looking in. He has great set ups into detonate and the unreactable OH pounce is a great option. However without meter he's no power house and has no convenient ways to build it. And in a game with massive damages off 50/50's using detonation isn't always going to be the best available option.
Hunter has the Hard to Blockables, the Sub Zero-esque nj4 game, decent mixup potential, and roughly similar damage. And better space control with trap and disc. Can even counter zone with EX Trap. The best thing about warrior though is the REALLY fast Armored launcher. Albeit SUPER Unsafe on block, unlike a lot of the casts armor. Warrior to me is much like High Tech Jaqui. On paper and in theory of "everything going right" the character snowballs like no one's business. However what character in MKX does that logic NOT apply to?
I have serious advice for Predator (or Pewdator) players. Stop waking up. Hold that on knockdown, even when you have to guess 50/50. You do the same to everyone else, so it's kinda fair. However you can still armor in other situations, for example if a Cassie does B12*4 or 33*2, make a read and armor through the gap. She can't block it if she decides to go for the plus frame, and of course your armor won't be broken. Learn how to counterpoke. If you want to win don't pick Warrior just because it has better armor, you cannot win with than garbage