To open, I'd like to get a discussion going about a wide variety of MMO mechanics, but part 1 is going to be about healing.
I wanted to start with healing because it is the most reactionary mechanics in the Holy Trinity of RPGs, and I think there is a great variety of fundamental changes that can be made to the system that will benefit players and be fun.
Lets begin with mechanics basics, then move into resource management, damage and special ability functions.
Fundamentally, healing is about keeping your friends alive and being valuable to the group, which is fun. Soloing as a healer is usually not fun. Healing is very reactionary, and if your buddies' green bar doesn't move, you often run short on buttons to press.
As far as actually mechanics are concerned, there are a number of usual suspects in the healing ability game. Short cast time direct heals, long cast time direct heals, instant Heal over Time, cast time Heal over Time, instant direct heal, and aura healing. We'll place things like absorbs, immunities, and dispelling under the special ability heading.
What type of healing mechanic do you find most fun? I personally like to queue up a short cast time direct heal followed by an instant cast heal over time. Something about that sequence says "I got you man" to me. Healers with nothing but direct heals are probably the most boring and reactionary. You don't spend your free time loading up the HoTs or auras or absorbs, you wait for the green bar to get smaller, then you make it bigger.
In most MMOs, the resource of the healer is of a large pool, slow depletion, slow regeneration type. It behooves the healer to get this pool as big as possible, so they can heal for longer without reaching the most dreaded state of a healer: being Out Of Mana.
Being OOM is one of the mechanics I would most like to change in future MMO gaming. Running around in circles, useless, while your buddies slowly(or quickly) die, hoping to get maybe one heal off is just a terrible feeling.
I'd like to implement a small pool, fast depletion, fast regeneration system for healers. Think Energy. The healer can spam heal only 3 or 4 heals in a row before OOMing, but in a matter of seconds they can cast again. To make this work, not all heals would use Energy. Perhaps the cast-time heals that require the healer to stand still for a period of time either cost no Energy or regenerate it. Proper management could look like keeping the pool half-full by mixing Energy generating and depleting abilities, or blowing through Energy and then pooling with your non-Energy depleting abilities in a sort of full-empty-full-empty undulation.