That was a very minor change to stop mastery scaling getting out of control, which now most paladins bypass by gemming pure mastery in the space of spirit. Spell interaction with mastery remained unchanged, whereas changes you are suggesting, of which are vague anyway, are a bit more indepth than a small mastery scaling change.
Even with the current 5.4 changes, our mastery scaling I believe wouldn't need changing since unless you can get a cast off on everyone before the 15 seconds are up of IH then the 5.2/5.3 level of shielding will not exist anymore, unless you are willing to burn mana just to keep it so, or you have complete control of raid position to optimize HR usage.