He's probably rational, but he's certainly not democratically elected and has ousted all his enemies. What do you define as a dictator? He's accountable to no one.
He is a dictator who has surrounded himself with yes men and purged everyone else.
This looks more like a description of Trump...
It is a spectrum not a yes/no answer.
Even rational actors may make bad decisions if they are badly informed, and given how risky it usually is to bring bad news to the emperor, chances are that Xi is fed with data that is a bit rosier than it should.
It is rational for a dictator to increase their power at the expense of some prosperity of the populace. Communist rulers around the world exhibited this trait, but non-Communist rulers also did the same from times immemorial.