I did that once. Was rein and got no heals at the start, I was only one on payload. Same thing happened again, flamed healer and when it ended I saw they did 12k heals. Felt like a right dick
rule of thumb, you're doing your job as a healer if you do roughly 1k healing per min. if the game so far was 8 minutes, GREAT did your job, some healers can go up to 1.3k average, and it's fun