My guess is the partition info is corrupt if it can't or won't update it, this is something I'm not sure that can be Re-Written, especially as with this device being S-ON. This would leave all the partitions intact but the partition info maybe pointing to the wrong places making it unable to write a partition (as with the system - it is there but unable to alter it) and giving failures as the images are what it believes are too large, small etc. even if it reads the boot/recovery/system partition and images.
Was it showing this previous to trying DIAG?
If so then I don't think you can flash the Boot/Recovery.images whilst it is Locked.
If it was stated as being Unlocked then it's been Relocked for definite (mine is still unlocked after using DIAG+.img's so I'm inclined not to think DIAG has relocked it as it requires a TOKEN ID from htc not included in DIAG), possibly making it (from public standpoint) unrecoverable without sending to htc or possibly using JTAG etc.
I would be inclined to contact htc and see how it stands on gaining Bootloader Unlocked in it's current state as you need the Unlock Token which I think you need the system up and running but they could hold the Token ID with Serial# IMEI etc when you request the Bootloader Unlock Token but I suspect they'll not want us knowing how