Prot Paladin was my second challenge and first tank. I did unholy DK first which was a goddamn joke with Prydaz. I think I was like 905 on dk. Prot Paladin I was 930ish and struggled. Then it just clicked and happened. You’re right though, you can get fucked easily. It really pissed me off that I came in a week later at 920 on DK and did Blood in less than 15 attempts. Most of those were wipes to Velen dying from aggro until I just decided to pay better attention.
Vengeance DH is supposedly easiest but i found it a little harder than DK. Most likely due to my relative lack of familiarity with the class. Neither touched how ass-raped I felt on the prot Paladin.
Hell, I sorta struggled on sigyrn with Ret. No idea why. It’s stupid fucking easy. Took me a few hours when others were done in a few attempts.