Stepping in with X isn’t always reliable. You first have to be sure that they’re truly going to go through with a charge attack, instead of doing things like flying kicks, teleports, canceled charges, etc. If they fake a charge attack, it’s very easy to use basic square hits afterwards, or they can fire a ki blast to completely nullify a step in. Stepping in with X can be very reliable against giant characters though.
Also, swaying on it’s own isn’t effective against rush combos. You can’t block immediately after a sway, so if you sway in the middle of a rush combo, you’re going to get hit. If your character has swaying in combination with a ground slash, gut stun, flying kicks, invisible ki blast or lift strike, then it’s deadly. Otherwise, swaying on its own is meant to dodge single hit attacks. Also, if a character can only sway in combination with those power attacks, it can actually be a dead give away as to what you’ll do. If you see Base Goku swaying from a step in, you know for sure he’s gonna go for a gut stun. But with SSj2 Goku, you won’t know if he’s gonna ground slash, gut stun or lift strike. Huge difference there.
And there’s far more differences than blast moves and transformations between characters. I just explained how Base Goku and Piccolo are a bit different. Here are just a few things to also consider:
What the characters do from a parry stance (do they parry and grab, parry and attack, teleport, or sway)
What triangle options do the characters have from basic rush combo hits (because believe it or not, when and where you can perform a certain triangle hit can have a huge effect when attacking)
If the character can step in, do they sway before using any of the power attacks, what move (flying kicks, invisible ki blast, gut stun) do they do with just hitting triangle?
There’s alot of differences in the overall movesets. Some characters will be really similar. But some characters are VERY different from others. Saying Majin Vegeta is a clone of Burter is absolute madness.
Also, what are some of those broken combos? I play against my cousin every once in awhile, and even when I combo into a step in, and use the second rush combo and go for power moves, he’ll actually end up teleporting some of my power attacks. If I hit him up in the air with a lift strike, and he enters the recovering frames, I instantly go for a finishing move, but he somehow teleports out of the way. I can get pretty high combos with guys like Chiaotzu though, because its really easy to chain uncharged square attacks together with rush combo hits.