Only thing left to try would be doing a switcharoo with enhancements to indirectly trade shield rating for main stat.
Considering the terrible returns Guardians get from Shield rating, I've contemplated recommending this, if only because Endurance otherwise comes at the cost of Strength which will bolster both threat *and* mitigation.
On an unrelated note, assuming a hybrid build using force scream on cooldown, how does endurance compare to strength?
Endurance compared to pretty much any stat errs on the side of the other stat after you've achieved the minimum hp required. This is even more true for Guardians wherein you have the wonderful benefit of treating Strength as a mitigation stat to some extent because of Blade Barrier. However, the conversion rate between Strength and the absorb of Blade Barrier is pretty friggin' terrible and is only really apparent if/when you analyze damage taken over the course of an extended period of time so it's not going to be a major game changer. The bigger benefit is, honestly, going to be the increased damage and threat generation.