Master of Death seems a bit worse for pet builds compared to say Bonds of Bysmiel and Primal Bond. While it is the main pet buffing skill of the Necromancer class, the conversion on it makes it a bad pick for builds that convert phys damage such as builds using Korvaak’s burning blade : https://www.grimtools.com/db/items/12729 and Warden’s Judgement : https://www.grimtools.com/db/items/1933 or other forms of global conversion for skeletons/blight fiends and this seems a bit off.
Flat out removing the conversion could maybe brick some undeserving builds (though there are other sources of phys to vit such as marrow band rings (2x 25%- 50%) deathrite grips (25%) guardian of death’s gates(100%), bonescavenger gloves (50%)).
So I wanted to suggest making it a transmuter to Master of Death (similar to IEE) with 3 points needed for 20/40/60% phys to vit conversion for pets each. This may be a bit weird because it would make MoD the only Exclusive skill with a transmuter. If that is an issue then it could be added as a transmuter to Spectral Binding which should be fine as even Solael’s witchfire has a transmuter for pets. Though I am not sure if Crate is open to making additions to the masteries at this stage.