Tanker AC or HP?
 

What is the most important thing for Raid MT? AC or HP?

Probably AC until you start grouping with clerics that can complete heal then HP.

I'd go with the HP, atleast for leveling.

what I want to know is that AC or HP which is better for raid MT not during a leveling.
let me edit the question.

AC is better for mobs with a high DI
HP is better for mobs with low DI

It's been mathematically proven AC is better in almost every situation as there just aren't many mobs in classic with abnormally high damage bonus and low DI.

Until much, much later on in the game: AC.

You want to get your worn AC above 300. Then put HP in every slot you possibly can. At higher levels some Stamina gear is a good alternative to HP gear in certain slots.

You need to hit that soft cap to mitigate as much as possible. For trash mobs it's no big deal but on bosses where you are getting multiple CH's per fight it's another story.

So AC is working properly here?

whats DI

I believe DI is damage interval...that is the max and minimum damage a mob can inflict on a single hit.

He might be talking about something else though...