I don't know much about wow-heroes, but I'm inclined to say that it isn't really helpful in terms of developing your character. It would take an awfully complex piece of software to do that, and as far as I know, wow-heroes and other gear score places/addons only look at item level. Item level is a great indicator of an item's value, but it is FAR from a rule. This is especially true with trinkets, though that may be mostly as result of their being some pretty OP low item level trinkets at the moment.
Rawr is dependent upon the individual class modules. Some are really good, and in those cases it truly is the "awfully complex piece of software" I mention above. Some are not so well recommended, from what I understand. I don't know much about the DK one, however. I'd definitely look into it though, as if is good for DKs, it will really do all the work for you... though of course you should pay attention as it does so you get educated in the process! :p
I use WoWWiki's page on enchantments for all my enchanting needs.
http://www.wowwiki.com/Enchantments_by_slot That wiki also has some randomly good info for more arcane mechanics that most people aren't at all interested in. :p
www.mmo-champion.com for all your WoW news.
TankSpot has become the top place for raid strategies as well, so make sure you don't miss that while you're there.