I don't think adding variety would be a nerf to healing. I'm not a healer, so take what I say with a grain of salt, but...
As an Archer, if I had my buffs, and Light Shot, I think I'd get bored spamming it in a fight. I think I'd get even more bored if I wasn't spamming it, but only hitting it every now and then.
It's kind of what healing is like at the moment. The subject of the thread isn't "Healing is too easy" it's "Why is healing so lame?". Sure, it makes it pretty easy. Personally I don't think enmity is a huge issue with healing. In most games your DD will get hate and lose the fight for you before your healer does. Generally as someone earlier mentioned healers pulling hate normally only happens at the start of a fight due to the tank or the healer doing something silly.
I'm more concerned about the 1 button to heal them all. Sure, you have buffs to worry about every 5 minutes, or less w/ stone skin and stuff, but let's say you have 2 people dedicated to healing, and one has buffing duty and the other is primarily healing or something. Man that's got to be -exciting-.
I think it would make things more interesting to have AOE spells and non-AOE spells, just like we have w/ WS's. All the same targeting as other job's WS skills could apply to healing as well. THM have the cone, CON have the circle, these could just be spell specific. Line targeted spells, while more situational could also be more potent or mana efficient, pulling healing strategy into attack formations, and causing healers that are really on their toes to just flat out be more efficient.
I think jobs that allow people to -really- shine when a high level of player skill is introduced is awesome, and while historically healers are an appreciated role, they aren't always given the opportunity to really shine.