You don't know how to mark targets I assume? Guarded targets can be killed by focused DPS. If you cannot coordinate this,this is a group issue/individual issue. As a tank in PvP,if I couldn't guard targets and actually fulfill my role,I'd stop queuing altogether to be honest. My Jugg tank is the only char I enjoy in PvP,guard switching keeps it interesting for me.
Find something actually worthwhile to whinge about.
Also...I NEVER see 4 tanks in a Warzone.Ever. I'm usually the only one. Was this something you saw once and decided it was the norm,if it even happened,or where you just playing against a tank who was great at guard switching?