Don't worry about hit rating in heroics. You only have a 5% chance to miss in the first place since bosses are level 82 only. More than half of that (3%) is covered through talents (Elemental Precision). Add another percent to that if you're Draenei. If you're still concerned, use some buff food to cover the rest.
There is also no difference in boss level between normal level 80 dungeons and heroic modes, so it really doesn't matter where you go. In fact, you'll have a hard time finding groups for normal mode instances other than ToC.
In between cloth, mail, leather items, and accessories, you can completely gear up a caster shaman by running ToC normal and heroic exclusively. The only items that will have to come from elsewhere are:
Totem - Get that from the Grizzly Hills PvP daylies. One hour "work" killing NPCs at most.
Off-Hand - The Inscription OH works well enough. On my server it runs for about 150 gold. Perfect until you get a shield.
Ring(s) - Don't spend lots of gold on epics. Crafted Runed Mana Band (Pvp Ring)works well enough for heroics and isn't even unique.
2nd Trinket - use whatever you can get your hands on.
Seriously, don't worry about heroics, and have nobody intimidate you with DPS numbers that seem completely out of reach. A year ago it was NORMAL to be around 1500-2000 dps and get things done. That people now do twice as much is not your fault as a fresh 80, and shouldn't concern you at all.
EDIT:
I am HEALING heroics as an offspec with gear that's very much exclusively from drops - and most of it from ToC. The only items I spent badges on so far (since everything went towards my Enhancement main spec) are the shield and the Chain Heal totem which I am switching with the LHW one depending on our group setup. If you look at unbuffed numbers from the armory, you'll see that I might very well play elemental with this and still do decent damage.
http://armory.wow-europe.com/character-sheet.xml?r=Defias+Brotherhood&cn=Antjhni&gn=The+Woodruff+Circle
(trying to stay logged out with caster gear for a day or 2 to give you a chance to look)
Edited, Nov 17th 2009 12:01pm by Kanngarnix