ldo transient response normal
Decrease the output impedence I mean,
For your case main pole is the output of error amp,
As you said you have add a miller cap 3pF that is large enough, it can feed the output ac voltage back to the gate of PMOSFET pass element, which is divide by the Cgs of the PMOSFET, multi by PMOSFET gm can generate ac current to make the transient response faster.
For more feedback ac voltage, you can try to minimize the area of PMOSFET to minimize the Cgs.
Another way to decrease output impedence is to add a cap at the output, you can use moscap to minimize its area.But in my opinion, because of the miller cap feedback, the output cap impedence can not be small enough until GHz range (for 10pF as a instance).
To enlarge the gainbandwidth is also a method to make transient responce faster, but it need large power consumption, and loop stability is also a consideration.
Use fast transient loop maybe not useful for your case main pole is at error amp output.
Thx