Well I am a little bit late and you probably already have choosen a healing class, but I'll answer either way in case someone else also reads this thread. The easiest healer class is sorc/sage. They are very mobile (which really can be a life saver) and have a mix of burst heal and heal over time. They are easy because there are only a few abilities you have to keep an eye on (resurgance for the buff on all healing abilities and innervate for force management).
But since you ruled sorcerer out I'd say the 2nd easiest is the merc/mando. They have a very strong burst that can make someone from 10% health go back to full health in a very short time. Energy management can be difficult at times though and it can be a pain to keep multiple targets alive due to the weaker aoe heals (not that they are bad, but they can be lacking at times compared to the other two healers).
Operative/scoundrel can be difficult to use. They make heavy use of heals over time and that means that it requires more micro-management than a sorc/sage or merc/mando. It is also helps if you know certain boss fights (for pve) or are familiar with other classes (for pvp) as Heals over time take a little bit to kick in, which means you have to plan a little bit in advance. But if you know how to use operative/scoundrel you can make your team look invincible as they are really strong healers.
A final personal note though: I prefer to start with heals when I am around level 45-50 as they become somewhat enjoyable to me around these levels. With early healing you lack a lot of tools and that makes it more difficult and to me less enjoyable.
