Give Morde a flat amount to his shield passive again
Properly using Mordekaisers shield passive used to be more important before his rework. Stacking up your shield right as an enemy engaged mitigated a lot of damage. It scaled as a flat amount with levels, which rewarded him for snowballing and made him innately tanky while dealing damage.
The strong passive shield created a fantasy of an "unkillable" death knight, who only got stronger as he fought people (as long as he could be in range of them). Now it is directly tied to his health and doesn't feel nearly as important as his W heal, which is an awkward and cheesy ability to use (I despise the delay on the heal).
The shield as a percentage of his health isn't terrible, but giving him a flat amount based on his level would give him a bit of help earlier, and as the champion with one of the most abysmal base stats I think he needs it.