There's always the lesser (300-500)/Greater (1950-3250)/Major (2800-4000) Holy Protection (Absorption) potions out there......
But you cant trade with some1 in a different realm making those a bit pointless
if it's a matter of Battlegrounds you're referring to, Kazzoo I reccomend strongly looking into a pre-made but I agree that when you're doing randoms cross-realm it's lousy not to be able to trade non conjured items such as pots.
I just relize that theres no holy resistance but there is holy damage. That seems a bit unfair for most classes cause they have to deal holy damage all on there own making pallys and disc priests a bit overpowered. And look if its becausethe priests are a least favored class or thats theres like not much pally classes in the game then fine i guess i got it but that doesnt really change the fact that there will never be resistance to holy damage (unless your a blood elf i guess you might have resistance to holy due to that all around resistance thing they got.)