You don't need a parser for that. Groups require group effort in order to run efficient, and you've played long enough to know when this is/isn't happening. When a group gets a clear with relative ease, you can be assured that you and your party are performing optimally, and the reverse is true as well. A parser puts a number on your performance, and this number doesn't tell everything. A parser helps a player improve very much the same way a step counter helps a person lose weight.
If you want to know how well you did/are doing, I recommend taking a video and then view it. You will see everything you did well, along with your mistakes, and things you can improve on. You will be able to see the performances of your party as well. If your DPS is down because the tank spun the boss, the video will show that. A personal parser will not.
I don't really play DPS jobs and definitely don't raid with them, so I know it is difficult for me to relate to the numbers obsession. I still care about causing as much damage as possible when doing DPS of any kind, and I know that if I am well-geared and optimizing rotations, I am meeting my own DPS requirements for the instance. If I looked at parser results afterwards, it would only confirm what I already know.