I was intimidated to heal at first, too, but the key is to learn by doing. I initially picked up WHM on my main (Senah) because I already had all the DPS jobs at 50 and I wasn't ready to try tanking. Eventually I ended up playing WHM a lot because we would always have a tank and DPS but not a healer online. When I did ok on stuff like Halatali hard I became more confident. The thing that helped most was trying to do a Brayflox HM speed run when I was still only i77. It was rough but I did it, and honestly most other content feels like a cakewalk compared to the stress of healing through speedruns. I tackled CT and all the other 8 man content I had access to, and discovered I love being a healer. If my FC didn't already have two healers for our static I would probably main healers on both of my characters.