Don´t know Android 21, but Beerus and Broly are getting passively depowered, drained and killed by Hades presence. Regulus copy every power from the enemy team and his own, blitzes and oneshots with a combination of hax. Seiya is the weakest link here, his abilities aren´t really impressive, except his last feats in Episode G, when oneshotting a Titan. Since we don´t know how that happend exactly, i wouldn´t make a decision for him in this battle. For Hades and Leo, yeah stomps. No matter how fast you can argue for DB, Regulus is literally omnipresent at the end. You can argue DBH against Saint Seiya, but not DBS, which isn´t even close to the SS top and god tiers.