try it out on tager first. for me, taokaka is the hardest to pull this combo off.
delay your 623D for like 0.5-1.0 second, which should be stated in the combo. this will allow the opponent to be released from the 4D~A hitstun, raising them higher so you can have more time to connect the j.6D~D. if you're having problems connecting the delayed 623D, give yourself some space before 5C at the beginning