is this legal?

I am calmly taking flight routes and I am killed by approximately 5 Alliance Players who are Hunters. But I realize that it is someone using multi-account to do this and it is a disadvantage in the game.
Postscript I am using Google Translator to claim

It's legal.

this guy was griefing people out in stonard too, he brought the black elite dragon and let it loose inside, then 6 hunter pets were running around targetting lowbies

Same experience, got a 5man team griefing Un'Goro flight path for hours:

Reported, but staff ignored the griefing part and just responded that multiboxing is okay.

I guess just kill on sight wherever possible.

I don't have the problem with the multiboxing part, it's the griefing part that is bad.

There's no griefing, this is a PvP server.

Not Illegal, its world pvp, accept it or go find another 10k populated server that is PvE... XD Good Luck!

Thanks , that's nice to know, thought area denying was bannable.