Regeneration is a quite balanced Team.

Demon King Piccolo and Cell improved this Tag in many ways. Mainly, the former made the Team very consistent at generating a early Game Rising Rush, which is extremely impactful for Regeneration since SP Perfect Cell (Revived) RED and SP Good Buu GRN are so hard to kill, that being in a 3 vs 2 situation by mid game is quite common for this Team.

In fact, Cell is the first Fighter in the Game ever whose “resurrection” can’t be denied in any way, unlike Endurance Fighters that get countered by Anti-Endurance Effect. That aspect of his kit, in combination with his sub count reduction mechanic, makes safely launching a Rising Rush very hard for the opponent.

The new Cell also brings the Team a lot of value in Late Game, by being a tremendous Offensive Fighter post resurrection, that can control the flow of the Game thanks to his Blast Armor Special Move and his Extra Move that can immobilize.

SP Android #21 PUR completes the Team nicely as she’s still a very solid Purple option thanks to her great Offense in combination with her halved Sub count.

This Team's issue basically is that SP SSJ2 Gohan RED directly counters it by nullifying most of its good things, so until Regeneration gets a good Blue Fighter, it's unlikely that they'll become Top Tier in the Meta again.