While I do agree it is great to have Sendai actually tested, after a few matches, I feel that there was a reason why it was initially banned.
She does have her faults (50 Speed is junk, weaknesses to Nature, Water, and Reason bite), but the main problem is that her offensive prowess combined with her excellent defenses make her terribly hard to crack. 120/100/110 Defenses are extremely high - on par with or better than most of the Defense puppet forms in the game. To put that bulk into perspective, I saw a match (don't have the log, unfortunately, so I can't prove it although there were witnesses) where she took three STAB super effective attacks consecutively with no recovery in between except for Leftovers and she didn't die. And she also has 130 Attack, a STAB combination resisted by one form of Puppet (Hatate), the ability to stat up with Curse and abuse it with priority, which makes her terrible Speed less of an issue.
Yikes.
It'll probably take more testing before we can reach a final decision, but I'm leaning towards broken right now.