What is with people?

[Vidu]

you cant report ppl because he cant play properly. OP cant play tank properly not because he want to insult the rest of party,he just dont understand how to tank.
there is no reason to ban OP if they report to GM anyway.

what will GM say if ppl who cant play properly in GM jail if that thing is reportable? "Sorry you are banned for 7 days because you are not git gut"?(joke aside)

First off: You can obviously try to report anyone for anything, if you believe there is a reason to. (and as long as you do it in "good faith", aka actually having reason to believe that there is something going on, I dont think it would cause as abuse of the report function - see something fishy? Report it - if it turns out that it wasnt a poorly programmed bot but someones cat accidently stepping all over the keyboard, it wont be an issue)

Second: The problem here is that what the OP was doing can easly be classified as griefing and harrassment - stealing aggro, spinning the boss, not reacting to anything said in partychat, wiping the party as result of all of this... thats all behaviour someone who would be intentionally griefing the party would show aswell and you cant really tell (in the moment) which is which. He wouldnt be reported because he played bad but because he played in a way that was harmful for the party.

And sorry, "he just dont understand to tank" doesnt really fly as an excuse when we're talking about the current raidtier, even if its just NM. He had at the very least 10 previous raids and probably about 20 primal-fights or so to figure out that in a group with 2 tanks, one is the MT and the other one isnt supposed to steal aggro.
I dont think its a far fetched expectation to assume that someone who has reached Alphascape 3 is familiar with that basics of their job - and I mean basics, not worldfirstclearplay. Stuff like your rotation, the difference between tank-stance and off-stance for a tank, moving out of AoEs, knowing how to handle a stack marker
OP even said that himself:

Yeah i get what you mean, as for the whole learning your class that's something you should know before you reach endgame content.

...yet, he doesnt - or at least didnt when he entered that run.

I would have believed that a person playing like that was nothing but a troll and deserved a report for griefing, instead of assuming that its just someone who doesnt know better. Someone who doesnt know better simply shouldnt be in that content (and apparently even OP agrees to that), specially not when unwilling to take advice - which circles back to harrassment, in a broad sense of the word: Chosing to stay at a level of play that ruins runs for 3-23 people.