New Daiyu is a potential monster on defense and attack however you will have to choose where you want to use her. The rush is extremely potent as a full control taunt, reminiscent of 5* Fast Priya, especially since taunt was buffed by receiving 5AP extra each time you attacked by a taunted character. With two Daiyus on a def team it will be extremely frustrating to deal with.
Will you be trying to get Daiyu?
Even the 6* version of Daiyu will be great on an attack team due to the dual specialist skill she has as well as infection on her active skill. However you will most likely not want to raise her active if you intend on using her for def teams to keep attack teams locked.