Even this is a subjective question.
“HC” Leveling
(Group 1) To some (not all), “HC” = 1 Life. You can trade, you can use the AH, you can do everything you can do, normally, on non-HC servers. You just have 1 life.
(Group 2) To others, HC = 1 Life + Self Sufficiency. Meaning, no Trading, no AH, no Mail, etc. But, you’re allowed to group for dungeons and run those dungeons, once.
To me (specifically), “HC” means 1 Life + TOTAL and COMPLETE Self-sufficiency! Similar to Group 2, but you’re not allowed to group for dungeons, either. Figure out how to tackle it, solo.
“HC” Endgame
(Group 1) Same as their “HC” Leveling rules.
(Group 2) Same as their “HC” Leveling rules minus the “can only do the instance once” thing.
For me, I align with Group 1 more and think there should be a “‘HC’ Endgame” server, but I digress.
“Leveling” and “Endgame” have ALWAYS been TWO different cultures, and why I view them separately. And, I find most (not all) seek a “‘HC’ Endgame” than a “‘HC’ Leveling”.