When your Cometic head gasket failed - I believe it was a result of head and block surface finish being the cause - and certainly NOT the ARP head studs. The surface finish required for Cometic head: "head and deck surfaces be flat within 0.002 inch and have a 50RA-or-finer surface finish"
I do not recall you resurfacing the head and block deck before using the MLS gasket ( I could be wrong).

You mention the heads tendency to "lift" over 350 HP - the physical limitation of the bolt.
The ARP studs have a much higher yeild strength - how could they not be a benefit over factory stretch bolts?
The factory stretch bolts are stretching beyond their yield strength.