The answer to all gearing questions in WoW is always the same: it depends.
Getting to the point where you can effectively heal a heroic in WotLK is largely about spell power. The fights are fast and mana regen is not a problem with the fast cool-down on mana tide. So often taking the highest spell power point avaiable to you in some slots is the way to go, even in the 60's this can be true. But if your armor or stam drop too low, you'll be in trouble, so be very judicious in which pieces you decide to take leather or mail in. If you're walking around in a robe, you're probably making a mistake. But a cloth hat may be just what the doctor ordered.
As resto losing a bit of armor isn't a big deal, but losing alot is.
As for how to solo, take your one-hander and shield and think of yourself as a prot warrior with spells. Toss on earth shield, wade into 3 or 4 things (or pull them with spells), chain lightning them to get their attention, drop stoneskin, mana, and magma, start swinging your weapon. Cast a CL now and again to keep them off your totems, drop a heal on yourself and refresh earth shield as needed. Lava is fun and keep flametongue on the weapon. If your mana gets down to about half, flip to water shield till it's topped off again, use earth shock or wind shock to interrupt casters and bring them into melee range, and watch stuff die.
Single targets you're not particularly efficient, but with earth shield you make a pretty fair aoe tank against normal mobs a level or two beneath you.
Edited, Feb 9th 2009 12:42pm by kingpatzer