i played a match as a healer, the entire time i was using my healing to the maximum, and at the end i got 500 points?! me and the other healer were at the bottom of the team. even though we did really well.
Go for assists where safe to do so as well. This will boost your score. Also if there are objectives, focus on healing your allies who are on them. In conquest, heal people who are defending or attacking points. In onslaught, lend a hand with the command ship etc. Also if you buff people who go on to get lots of kills themselves, you get ribbons and big points! All of this will not only score you more, but make you a real asset to your team, although you sound like you are already one. Finally, score is important for earning them big monies, but if you are winning, and it's because of your healing, then your team will know this. w/l ratio is the most important personal stat out of them all IMO. Good luck to you!
In Onslaught you get fewer score for healing compared to TDM or Conquest.