Welcome to my Dragonknight Healer build! It's still a work in progress, but hopefully you'll find this useful and enjoyable. Using this build, I've been able to heal vet DLC dungeons and vet trials.
Enjoy!
Gear:
Monster sets:
Symphony of Blades: probably the strongest monster set for healers in the game. It increases group sustain as you heal.
Alternates include: troll king, earthgore, and, if you have a hard time keeping your magicka up, engine guardian.
Grand Rejuvenation: This procs increased resource regeneration on casting grand healing.
Master Architect: Procs major slayer on ult for a percentage of the ult cost. When used with War Horn, you get major slayer, major force, and better sustain. The five man cap makes this a little weak in trials, but it's perfect for any four man content.
Olorime: This procs major courage, buffing the group damage.
Note: perfected gear only provides a slightly larger magicka pool than non-perfected gear, so if you only have normal Olo, don't worry.
Alternate Trial set:
Stone-talker: This gives a nice buff for group sustain through heavy attacking. Not as strong as MA for four man content, but this is a nice set to break out for trials.
Alternate Non-trial gear:
Hollowfang: This is a decent sustain set with some built in healing. Not as good as Stone-talker, but quite solid.
Spell Power Cure: Arguably better than Olorime in some situations, this procs major courage on overheal.
Beginner gear:
If you're new to ESO and/or healing, Sanctuary and either Winter's Respite or Worm's Raiment make a good starting point, with Troll King as a monster set.
Backbar weapon: You can run either ice or lightning, depending on your preference and your group's need. As for enchantments, crusher, magicka drain, or a damage glyph all work.
Quick note on CP: the green CP have no effect on combat. Choose what you will there.
Frontbar run through:
1-3. Radiating Regeneration, Combat Prayer, Healing Springs. Basic healing staff abilities. Cast 'em often. Make sure to keep Combat Prayer up for minor berserk.
4. Engulfing Flames. Nice buff to group damage, but if your group is stam heavy with no DKs, this won't do much. You could swap to any of the options listed for BB #4. Alternately, you could use Noxious Breath for the debuff.
5. Obsidian Shard. This is your emergency burst heal. Very strong and has a great range. It can only heal up to two players, though.
Backbar run through
1. Energy Orb. Very important for group sustain, as DK healers don't get great synergy options.
2. Wall of Elements. Important debuff which also can proc Olorime. Can use ice or lightning staff, IMO.
3. Elemental Drain. Important for group sustain as it procs minor magickasteal.
4. Cauterize. This is flex slot, you can put a lot of things here. Options include: talons, for debuff; coagulating blood, for personal healing; DK armor or harness magicka, for survivability; igneous weapons, for the group buff; cinder storm, for AOE heals and Olo; Altar for group heals/synergy.
5. Fragmented Shield. This procs major mending and gives a good damage shield. It's very important for harder content.
For backbar ult, I often slot DK standard for simple dungeons if I have a good group.