Res is worth the point. Jewels of life spawn on most, if not all, the major stages and raids. Some actually consider maxing it so they don't waste MP healing them back up.
As for the 3 main attack skills:
Originally Posted by Fiona
If you only have room for one attack skill, then that skill should probably be Pieces. Pieces has a short ten second cooldown and is better for bosses than Holy Spirit.
Theoretically, if you have room for TWO attack skills, you should get Tears and Spirit instead. Then you'd have a skill that's probably better than Pieces for most (not all) bosses, and a skill that's better for Pieces against comboable enemies or large amounts of enemies.
Many healers don't have room for that, though.
1 into Concentrate is only worth it if you have truckloads of mana. Generally, your priority order should go MP Recovery, MP Increase, then Concentrate.
Critical is an absolute waste for an Eir, as many of their skills are multi-hit, weak skills, as opposed to Dainn's high-damage spells.
1 Sacred Wave
1 Moon Fog
Those two are "one-point wonder" AoE skills that will definitely help in doing damage to mobs.
Most Eirs recommend maxing Moon Bind for some of the peskier enemies, especially those who can't be combo'd.
Blessed Defense is useless. Blessed Bravery may help dish out a bit more damage, but you probably won't find the 4/7 extra points to be able to put in.
Some Eirs will grab level 1 Life Extension for added fake-res ability. People tend not to get the higher levels since buffs override each other.
Light Shield is a costly "panic button" if you and/or your party members are going to get crushed by an attack that you just can't avoid. I say costly because spider ropes and black pearls are the hardest reagents to farm. You'll be able to trade in Vouchers of Appreciation for reagents in some future patch, but who knows when that'll be.
</tossing out well-known info>
I don't have enough knowledge about heals since I don't actually play an Eir >_>;