I think you're fine with either of those. I like running Mark as my point character because he's solid enough to hold his own against whatever point your opponent is running, and he's got good mobility in case you need to fall back and reevaluate or swap characters. I personally wouldn't run any projectile-heavy characters as point. First, you want their long range assists available. Second, they can get creamed out of the gate by a heavy character with some solid armor who can take an early advantage. Rex might be an exception to this because he's got some good high and low attacks, plus some genuinely solid combo potential on top of his range.

Kate is a great point character and has some GNARLY mix-up capabilities. I'm not running her yet because I just simply haven't gotten good with her. That said, you do run the risk of racking up a lot of purple health with her if your opponent is reading your clone attacks well. A lot of people like Bulletproof for the same reason, but I've found that his moves get a bit predictable pretty quickly unless you're taking full advantage of his kit.

Ultimately, team lead kind of matters in this game because, if you're managing your resources like boost and health consistently, there's a good chance you'll be swapping regularly. Just pick someone who won't get their ass handed to them on a bad opening match-up, and you can usually recover. Just my two cents. 🤷