Birth by Sleep Ohai, me again.

I would like to know if KHV has any tips on beating

Spoiler

Xehanort in Terra's body

 

First, Once-More/Second-Chance/Renewal-Block are all must haves. Second, you can block anything except when he decides that his keyblade makes a good cannon; that you just need to run from. It is a long and grueling battle but once you get down how he works you will rarely need to heal because renewal block will take care of your dammage. Just continuously block and counter. Note that he does have a combo designed to get out of once more (The one that ends with his dark hand), if you get caught in it spam dodge because remaining in there will kill you. That's about it. Throw in a few shotlocks if he isn't moving much.

As a side note, do you have all four of his reports? Terra's Mirage Arena one is commonly missed and I doubt you want to have to fight him again for that.