I took my level 20 Barbarian (Rend, Frenzy, Charge, Shouts) with 2 crappy legendary items and finished Kor Dragan and the level 30 monsters / elites didn’t drop anything worthwhile.
But just saw this video:
Apparently you can just run in and loot chests and corpses, then log out and repeat.
If you finish Kor Dragan the strong hold cannot be farmed anymore, so keep it open.
(Not sure why Blizzard capped it at 20, it’s pretty stale)