Maybe I've been a DM for too long, but if I saw one of these coming to my campaign, the words that would scare me the most are "and magic effects". A lot of classic D&D monsters use "and magic effects" which this guy can block with a ward that can't be dispelled and does not require Concentration. Plus, this isn't 3rd Edition, I don't have a running list of which monster attacks are "and magic effects" although I suspect that's most of them. And Advantage on their already strong Wis/Cha saves means there's little to no risk of failing.

I get that you're trying to mix up the Rock Fighter/Scissors Rogue/Paper Mage up, and I like the flavor. We've seen it before, and it would be a good part of atmosphere building. But it could lead to a lot of unexpected encounters being trivialized. And I'm shuddering at the thought of one of these guys taking Proficient in Dex saves, which even assuming a Dex of 10, bless spell and ring of protection, means a 7th level such paladin will make the DC 18 save of adult black dragon breath (CR 14 and way above his pay grade) 70% of the time, taking no damage. His buddy, a 7th level rogue with the same bless and ring but a Dex of 18 makes the save less often. To use an even funnier example, such a paladin could tank the Death Throes of a Balor at point-blank range with a 57.75% chance of taking zero damage, while the rogue has a literal 50/50 shot.

Is there any chance I can persuade you to scrub "and magic effects", or make at least make it more specific? I'm just worried that this archetype's intended use doesn't become a massive unintended headache.