Guild Wars 2

So I’m new to WvW and have been going on teamspeak to follow the commander on comms.

I often hear the commander say “stab one” or sometimes “stab two”, what do these mean?

Some other questions:

It seems like Guardians, Necros and Eles are the 3 core classes in a zerg with maybe one or two Revs. Are the other classes utterly pointless then in a WvW zerg?

Finally. Is metabattle still a good place to get my WvW builds? I play Guardian and the meta section says AH Frontliner, with celestial armour pieces which I can’t get. Is this build dated or is it still the standard?

On my EU account I want to join a good WvW server. The next 5 servers after these are French and German.
Is there any major differences between Far Shiverpeak and Desolation servers? Is there anything I should know before choosing which to join? Which has been a top tier server for the longest? (not that this bit will influence my decision much).

Just wondering what to choose. Thanks.