I have said how ardently I hate QQ. But here we go.
The Hard Knocks achievement is not impossible. For the most part. I got the WSG flag return on an 80 and a 74, the EotS flag respawns many times per game, and the AB points are in constant fluctuation.
These are battlegrounds with 10-15 players per team and flags that can respawn many times per game. Theoretically, every player in the battleground can get the achievement without sacrificing the game itself.
Alterac Valley is a different beast. 40 players, limited towers, no incentive to take your towers back to help the other side, and the shortest time limit.
Once you get the enemy towers, you'll find yourself sitting in them with 2-8 other players waiting for the enemy to show up and defend. You must pray that a) you're the fastest clicker and b) none of the others with you are jackasses waiting to kill the enemies that show up to defend. Which happened to me and several others.
All of those who want the achievement are sitting and waiting at the attacked towers, praying some kind soul on the other team will arrive to take it back. What this means is, nobody's coming to defend because there's no real gain to that. It doesn't give you the achievement (I know, I defended), and the people wanting to win the game don't need to defend as much as kill the final boss. (And, no, they won't stop or slow down to let people get the achievements.)
Out of 40 people, only about 6 managed to attack the 4 towers for my first game. It's pathetic.
Those in the battleground who are actually playing the game zip through and defeat the boss at the end because they meet no resistance.
80's who race forward and get the towers rarely stop to kill the mobs on the towers, so lower levels who want to wait and recap with their orphans get mercilessly killed by 79 mobs (I was in stealth and they still got me).
The only sure way to get this achievement is to have a completely flawless run to a tower and to not get targeted by any of the tower mobs (or have an ability that drops aggro).
All in all, the odds are overwhelming, the company is both competitive and sadistic, and the enemy is apathetic. I have no idea how anyone can succeed without astronomical luck or premades with an "understanding."