Enh Shamans and Rogues are using Dual Wield unfortunatly Hit Cap for Dual Wield is almost impossible to reach.

It's  (27%=886 hit rating so even if you will Gem all over for Hit you might not be able to reach it.

That's why for those classes we should only reach something what ppl usually call "soft hit cap"

Rogues:

Poison Cap :152 HR for Combat (with Precision) 214 for Mutilate HR (without Precision).

Of course more Hit Rating than those numbers  for rogues aint that bad,  you will always get some more White hits but it's not THAT needed.

Then we are coming into casters.

So basicly  hit cap for spells is (17%=446 Hit Rating)

It's also quite a high number. But a lot of casters have talent's which give them Hit % it depends on specc so check out your spec , maybe sometimes you can somehow change your talent spec to get more Hit.

Really Important is that on Raids you should always have a Boomkin or Shadow Priest, Those 2 classes bring Debuff on boss which reduce your chance to Miss by 3%, so basicly if you are raiding you need only 14% from talents/gear/gems.

Enh Shamans and DK's with Virulence 

Those classes are prety much MIX class, they used as much Spells as Melle.

DK's with Virulence need 14% [It's needed for applying their Diseases]

Enh Shaman basicly need 17% but dont get more then 14%[You need 17% for 25man raid, but in those you SHOULD have Boomkin/Shadow Priest so they give you 3% :>]

*********If you are in party with Dranei lower all those Hit caps by 1% [Heroic Presence]***********

What is Expertise Rating?

One point of expertise decreases the chance that melee attacks made by the player will be dodged or parried by 0.25%.

Expertise is used only by Melle Classes.

Exp cap is [26expertise= 214 expertise rating]  which gives 6.5% to reduce chance for your attacks to get Dogded or Parried. 

Due to fact that Bosses have 6.5% chance to dogde, and they cannot Parry from Behind, that amount of Expertise (while standing behind the boss) is enought for melle dps.

Tanks in the other hand, cannot stay behind the boss :) Not while tanking anyway.

Hard Cap of expertise  is 14% parry or 56 expertise (460 expertise rating).

It's other "cap" which is almost impossible to get :>

And it's not that needed for true. None tanks are gemming/enchanting for Expertise it's a stat which just increase your Threat, that's all :>

Defence Rating

That's THE MOST important stat for tanks. In the beggining anyway, after you gear up you shouldnt have any problems with it :)

Defence rating reduce the chance to get hit by a boss by a critical strike.

Critical Hit immunity for a level 80 player against a raid boss occurs at 540 Defense.

Any Defence point over that number is not "lost" obviously cause , defence rating increase your chance to miss boss attacks, to dogde and parry them aswell. BUT it's not that good stat as e.g Stamina :>

So dont gem for Defence Unless you really need it :>

Feral Druids are not gemmin/gearing into Defence.

Just put 3/3 into Survival of the Fittest in Feral Tree to be Def Capped ;>

That would be all I believe what I wanted to say/write :>