Getting this achievement legit involved quite a bit of skill and luck. You need to be able to block well however you also need a team that are good at dispatching opponents. I would suggest staying at the far end of the map from the enemy spawn as possible to keep the opponents travelling as much as possible.
I personally had around 5 knights standing around me so even if some enemies got through my bodyguards they were severely weakening so I could take them down with one swing. So this achievement is a lot easier when your team actually uses teamwork to protect you.