I concur with the eternally doomed marsupial. I believe strongly that Corvus personally healing his brother has a stronger link than some random doctor dude. It may well push the line of success or failure over the edge into success.
Once again, I remind you all that the Laws of Narrative are in play and while we haven't precisely divined the laws (and really, I think after we establish the outcome of this current issue, we need to get around to divining them!), I am quite aware, as a writer, of how they interact. Here, the fact that a brother of Guilliman has seen fit to personally use his skills to heal him is narratively important.
Worst comes to worst, just ask Durin to confirm it.