Nostalrius Begins - Quality wow vanilla realm (1.12)

I know this sounds weird but the way it happens is that everytime i'm in a group, for example, a 5 man for deadmines, i get massive lag (around 1.5kms) which i've noticed not only interferes with the game,but also with my whole connection, when i get massive lag in Nost, my whole net slows down to the point my skype calls drop.

Now whenever i'm questing i have around 100-120ms, which is fine.

What could be the cause of this issue? I've tried both realmlists and only running Nost on my pc and i get the same results whenever i'm in a group

i'll never be able to tank or do world pvp :c