This is not an actual solution but a heads up, it aint enough to be the highest scoring player as the jaguar in a session, your team must also win the match.
This doesn't work in a private match, it has to be done in a Public domination game session or the achievement wont unlock.
You have to wait until you get to a match where your team is playing as the Jaguar for this achievement which is annoying. My way was to be in a match until it ended and hope it was my turn to choose character for my team. You could also just quit the match and search again if you didn't get the Jaguar.
What I did to score big in domination (I suck at it, never plays it) was to be offensive and attack. You get 200 points for capturing a checkpoint. When I saw a checkpoint being attacked by my team I run there as fast as I could and hide in the area.
When we almost captured the checkpoint i stunned a defender and then directly when we have captured the checkpoint I killed the stunned player for high points.
Disguise is a great ability to hide in the opponents checkpoint.
I don't think playing defensive and wait in your own checkpoint is a good way to rack up points, because sometimes it takes forever for the checkpoint to be attacked and you need to win the match so better to be offensive and try to always capture the checkpoints.
Hope this helps a little towards this annoying achievement.