Kick a dog enough times, its going to bite back.
I've fought a lot of Terumi's with Ragna, your general game plan is to get in and stay in. I know that's easier said than done given Ragna's superior neutral game, but ya'll got dat new 5D buff. You can confirm that 236D and get knockdown pretty quick.
If he locks you down, don't use the counter, seriously don't, it sucks against Ragna; he can divide through it, grab it, or 6D it. If you have to use a reversal, use either CA or Soutenjin.