I blame 3 games to 1600 sweats, 1 to hax, 2 to skill issue.
Dunno what I’ll vote, there are positive effects and negative effects that Terastallization gives.
Defensively, it can give you the chance to live an otherwise super effective hit if you time it perfectly, it can give an overall better type MU against the rest of the opponent’s team, and can even do a bit of self-proofing.
Offensively, however, 3 STABs or 1 STAB + 1 super charged STAB is incredibly strong and the havoc it does has even surprised me. It can break through otherwise strong defensive cores or plow through the enemy team in general.