ideally you want it to be roughly 50/50

that is, min ilvl and new folks, you heal about 60% of your buttons and dps 40% as you get more experienced, ilvl boosts, mechanics learnt etc, it would graduate more to 40:60

whats important is that it is fun and you have a variable and significant enough portion of your kit be not healing, ie dps, support, buffing etc