I think that too much hp is also being destroyed in his base form as well.  I noticed that 60% of his max hp was destroyed at one point.  I thought the cap was supposed to be 40%.

This sounds like it's likely a visual bug as there is a 25% cap on max HP destroyed by Decay. Would it be possible to get a video of this?

I already ran my key for this week but here is a picture.  I do not believe that this is just a visual bug because he dies very easily when his max hp has been decreased that much.  I believe that the bug related to the HP scaling on his a2.

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I do not have a picture but when he switches to his alternate form, his max hp decreases because he no longer gets the stat benefit from his A2 scaling but the amount of destroyed HP seems to remain the same numerical value causing his overall max hp to 1 and he then dies in 1 hit.

Completely understand. 

The issue comes in that without seeing this in practice it's really tough to assess whether it's visual or not. As of now, there seems to be no known bugs with Toshiro, hence wanting to see it in practice. :)

That said, I'll pass this along up the command chain and let you know if I hear anything back. I may DM you/ping you in this thread to grab additional details too.