Correct that is an area of the game I don’t have any interest in competing in.
You don’t have to do it to realize that almost all damage in PvP is magical and Tanks take 50% increased dmg in PvP yet Prot Pal is able to easily mitigate magic dmg. So the harshest magic dmg environment is in fact PvP yet Prot Pal thrives I wonder why 
Yea you can and that is why the #1 parse on mythic Maut months ago was a Block capped mastery Prot Pal. Which keep in mind while also being block capped your dmg reduction standing in Concentration is 55+% flat dmg reduction to go with block.
To say Prot Pal is objectively weak against magic when you can 100% spec to nullify it makes this claim false.
If there was an entire Mythic that had 100% magic dmg Prot Pal could cruise through it as if it was physical if you spec that way. It’s their strength not weakness. Then lets not forget they have way more big buttons to press against magic if for some strange reason they need them. That is why they can continuously mitigate magic with nigh immunity.
I didn’t derail it I only provided a simple answer then the usual suspects made ridiculous claims.
It would be great if we could just talk about how Prot warriors are weak against magic and possible solutions. If the solutions don’t sound attractive then I have enjoyed Prot Pal since it’s OP against magic. Seriously lets focus on Prot Warriors please and thanks. They need some buffs.