A very easy way to get this achievement is in the Team Deathmatch portion of Battlegrounds (currently it is random which game type you will play, so just keep playing until you get Team Deathmatch).
**Edit**You now have the option to select a playlist. Your going to have a better shot with this method in Team Deathmatch due to the high point value awarded for assists***
Now, if you are a seasoned vet and dish out a lot of damage you can get this simply by getting loads of kills in deathmatch and you will likely be above 3000 points.
However, if you are not the best at PVP (or simply don't like it) and have difficulty getting kills there is an easy way for you to still get the achievement. First, equip several AOE skills to your skill bar (as well as a protection skill and a way to heal yourself). Go into areas (stick with your teamates) where there is a lot of fighthing going on a drop all your AOEs on the group. Now, even if they are not strong enough to get the kills, simply doing damage will get you assists if anyone (doesn't even have to be on your team) kills the player that you have done some damage to. You will get 100 points for each assist (the same amount as a kill!!). With this method you should land loads of assists and a few kills here and there. Top that will other random medals you will get during the game and you should easily be above 3000. Cheers!