Paladin would much rather use Aldor Peacekeeper than Scarlet Purifier. Also when running that card it makes it where you can't run other deathrattle minions. And you can't play it into haunted creaper and nurubian egg.
Not good enought, since DR minions with 2hp r scarce, so it is usually only 4/3 body which is kinda wasted deck slot, but sure it can be a tech card in your specific meta/rank, but overall its just not good enough to see consistent play ;-)
Everyone will run Purifier, if it did 3 damage instead of 2. 2 damage just doesn't kill anyone besides mad scientists, and normally you don't want to kill enemy scientists. There was a cool deck concept named eggladin (you get the idea), but aside from that people didn't had much with Scarlet purifier.
I ran it in a shockadin with two Muster for Battles, worked wonders for me. Especially against hunters it almost clear their entire board, getting rid of the infamous Haunted Creeper/Knife Juggler pings was nice. But this was all pre BRM, and got my Pali golden in about six weeks with the deck, which included 2 Scarlet Purifiers. Even against the Piloted Shredder it's quite amazing often having your foot soldier or your Muster for Battle weapon/Truesilver to finish the board off. Ran one Quartermaster in the deck, not even a single Consecrate.
And just to add some spice; my secret ingredient was Captain Greenskin. Helped a lot on buffing your Truesilver into Sludgekilling material, and I even often used it on the 1/1 Muster for battle weapon.
But back to the point; I'm not sure how it is after BRM, haven't played Paladin in a while, let alone ranked. But I definitely used him a lot.