I just made 80 and I want to be able to do raids I have been told rather rudely that I need a DEF score of 540 to do heroic instances. My question is how or where do I go to get the high goal of 540? Do I continue to do non heroic instances in hopes of better gear? Thanks in advance for any suggestions on this topic.
Firstly, you do not, in fact, need to be at 540 defense for heroic 5 man dungeons at level 80. The defense cap for these dungeons in 535 currently. That said, you do need to be at 540 in order to tank Raids. What these defense 'caps' ensure is that you aren't critically hit while tanking, causing what would likely be your death and an ensuing wipe.
My suggestion is the same I make when a guildie asks about getting ready to tank. Start with the normal instances for ToC, FoS, PoS and maybe HoR (this one is a real bugger most days) and get yourself some decent gear. Once you're at the defense cap for heroics, you can move on to them and work your way towards the 540 you need for raiding. So for now, guildies and the Dungeon Finder can be your best friends.
What this accomplishes is not only getting you egared, but experience in tanking situations. Gear i the simple part of the whole puzzle, experience is what tends to be much more valuable and much harder to come by.
to get to that all important 535 def rating to raid, don't forget that you can make some significant jumps through item enchants or potions. Throw on an Elixir of might defense and your def rating shoots up by 45 for an hour. you can easily gain 150 points which may help you get there if you are close.
You can get easy 540 def by using BS crafted blues: tempered saronite gear. This is low level gear of course but with tons of def rating. Saronite is cheap nowadays, any friendly miner will provide you with enough stacks within 20 mins. Once you have defense at the right spot grind heroics and buy triumph gear, and crafted ilvl 226 boots and belt and ilvl 245 chest and bracers (a bit expensive, need 8+4 crusader orbs, 15 triumphs each and some titansteel and eternals) and then ICC patterned ilvl264 boots and legs (very expensive, need 8+5 primordial saronite, about 1500g each). Meanwhile, as said above you will have the drops from reg and heroic ICC5 and ToC5. Also check the tankspots guid for initial tank gearing/enchanting and gemming.
Buy yourself a LOT of tissues, as a new low-geared tank you will be spit on by all these OH-LOOK-HOW_OP_I_AM deepses.
I hit 80 within a week of the expansion and was tanking heroics with a def of 515-520 with dps and healers also way under geared by todays standard. As long as you can hold threat and have a grp that either knows how to play or has the gear to just power though an instance anyways you'll be fine. You'll get enough badges to gear yourself so pugs will stop their QQ in a day or 2. Good Luck