I run content as healer and as tank. It isn't even which role I 'feel' I get more comms with; it is without any doubt whatsoever that I get more comms when I run stuff as healer. Does this mean I am a better healer than a tank? Whether I am or not, coming to this conclusion is inductive reasoning, and flawed logic.

You have to keep in mind that a commendation given to you might not be because of your performance. This person could simply like your name, your glams, that you explained mechanics for someone, or just randomly gave it before making an exit.

However, I cannot say with any certainty which healer parties favor more. Generally speaking, if you're keeping everyone up and also tossing out some offense, you will usually walk away from an instance with at least 1-2 comms, regardless of which healer you're using.