if your going to be a healer the first thing you should ask yourself is are you going to be the healer of your team or do you want to do massive damage? becuase in my opinion its not good to be both since you have to divide your points. i've been both. also
it kinda depends on your play style also, if you want to hang in the back and dont like to be hit that much, choose the healer so you can heal and buff teammates. if you want to be in the middle of the action skip healer all together and go for the heavy
Gender doesn't matter to combat or the overall story, just voice and a few dialog options.
Be whatever you want to be. Having said that... Just be wary of becoming a "jack-of-all-trades" -- getting both "Blood Mage" and "Spirit Healer" specializations is probably NOT a good idea. Also, it's probably best to fill out a single branch by level
16 or so.