This happened to me yesterday for the 1st time. I picked up a team mate's ballistic vest and went on as usual. A guard dog jumped me around a corner and as I almost instinctively started to press square to respawn I noticed that I didn't die. The dog just kind've bounced off of me as if I had a Riot Shield. I killed it and went about my business. Further investigation online tells me that the vests protect you from up to 3 dog attacks. Cool....learn something everyday.
It sucks playing against the vests for sure. But they serve their purpose, especially in hardcore. Food for thought: what idiot goes into a war without grenades, ext mags etc? They design the game so you have options for various loadouts.....if every player had every available option and streak automatically then there wouldn't be anything to unlock/work toward; and they'd have to start designer controllers with more buttons to use all the attachments/streaks/lethals etc.