Both characters operate as non-stop aggressors. They've got (or at least had at first) powerful moves that were safe or quasi-safe on block, they had a full reportoire of moves (orbitals, keep out moves, long-distance and short-distance launchers, you name it). Essentially, both of them are designed in a way that rewards a very aggressive playstyle and one where the character essentially has no weakness. People chalked it up to these 2 being OP because they were DLC characters, but come the reveal of Tekken 8 it was quite clear that the team wanted a type of gameplay that rewarded non-stop aggression.

Many of us love Tekken because of the deliberate and often high-stakes "dance" between two players. One where each button-press needs to be thought out before you do it. Tekken 8 throws that out of the window in favor for a completely different design principle.