Blood elf.
Normally in the bracket up here I'd suggest Tauren ( Increased 5% base HP; Stuns 5 enemies within 8y for 2 seconds, DRing with HoJ / FoJ ) , but Paladins don't gain their interrupt till early 50s if I recollect correctly. Given you're playing Retribution and not 'Prot', might prove invaluable in most scenarios.
Those who think Tauren, arguable, sure. Can interrupt a cast the same way, although the HoJ + Torrent combination doesn't give any DRs, and since we're talking Ret over Prot. Admittedly wouldn't know how much a difference the 5% HP would make, or if it would be worth the DRing /w Stomp constantly in 15-19.