Not a guide but some useful tips;
I was lucky enough to obtain this during the first day of release. I would recommend two of the following classes; Tactical or Heavy.
I personally utilised the Tactical Class for this achievement on ‘Seize Ground’. The reason being this has the Auspex Scan perk and allows you to see enemy players in choke points that you can defend with your team. Not to mention, I would say the Tactical is the most balanced and versatile class. I found it beneficial to stick with my team mates and select my engagement’s carefully. I used the default load out Bolt rifle and unlocked this during just my second game.
Other TA members are mentioning the Heavy Class as a strong alternative due to the Iron Halo ability and its immense firepower.
By all means, you can attempt to camp an enemy spawn if you have too, or as with the Tactical class, stay close to your team mates and play the objective. This is a team based game and requires each class and player to work together.
If you leave tips and tricks that could further help other TA members, please do. Until an easier alternative is found or private lobbies are introduced, I can see this achievement being a hard nut to crack for quite a few people.
I would also personally recommend the Seize Ground or Capture and Control Game modes.
If you're also going to downvote, at least specify why. GLHF