I feel like I'm doing something wrong, or not fundamentally understanding how the combat works. I got stuck on the last Raditz fight for almost an hour because I kept losing over and over to him. Granted, I was level 4 and he was level 6, but I just assumed that was okay since I did a decent amount of exploring/grinding and would have had to purposefully grind even more if I wanted to be any higher of a level.
I never seemed to get his stun meter even remotely below 90%, I don't really seem to know when I'm able to properly throw in the super attacks (I try at the end of a punch combo, but it doesn't really connect all the time), and Raditz seemed to have super armor constantly where I couldn't finish combo strings against him and had to continually just back off and wait until I had an opening again.
Was this fight supposed to be this much of a struggle?
Hmm, I'm trying to think of why you're struggling with that (not in a condescending way lol).
From what I've played, you can play fights fairly safe by just blocking. Obviously this doesn't work as well for his more 'special move' phases, but in normal fights your can just block, and either use burst if he's close, or vanish if he's far away, to ease the pressure or get an advantage.
With your melee combo, you can add a finisher with any face button, which gives a different effect. I can't remember which button does which lol, but one is a ki blast, one restores ki, and I don't know what the other one does. You can cancel into specials on the final hit of your combo, although some will just whiff because it knocks them too far away. Melee combo into a beam special is fairly consistent though.
Don't forget about the fact that if your ki and focus is charged, and you keep charging ki until that transition happens, until your focus meter runs down you can combo specials into each other, and you can charge up ki to fill that as well during that time. So you can throw out and combo like 4 kamehamehas at once.
In regards to stun, you can get stuff to increase that from the skill tree, and certain special moves are better for that.