To make a long story short: My warrior has been around since around patch 1.10, leveled as Arms, raided into MC as Arms. Took a break and rolled a Hunter for BC, only raided Kara, ZA, and the occassional Gruul's.
I respecced to Prot a few days ago and have since started collecting tanking gear. I bought the Faith in Felsteel set and a few other pieces off the AH to get me a quick start on some defense rating, but for some reason the +Str set bonus doesn't appear to trigger. Because of this, the Felsteel set has lost some of its appeal and I'm torn between 3 helms I now have: The Horseman's Helm, Felsteel Helm, Myrmidon's Headdress.
I obviously do not have a good tanking set, but we all have to start somewhere, right? I've been looking at AtlasLoot Enhanced and checking Wowhead for possible upgrades for the stuff I am currently wearing and I am seeing quite a bit of gear that would be nice upgrades from what I'm currently using. My druid friend (MT for my casual "raiding" guild on Boulderfist) said in a nutshell that my armor is too low (~12k), HP is too low (~10k unbuffed), and Defense is too low (409-421 depending on helm), but that I could do some of the easier Heroics and possibly some of the moderate Heroics with overgeared DPS and heals at this point.
I guess my real questions are: What is my highest priority for getting to a stage where I can "safely" tank Heroic 5-mans without putting too much stress on healers? What kind of numbers do I need for HP, Defense, and Armor? How much avoidance do I want before popping Shield Block? Is SBV or Block Rating more important? I have a very finite supply of gold at the moment, and I've gemmed all of my gear with just Uncommon quality gems because I figure gemming with Blues and Purples isn't worth it with the quality of my gear and how close Wrath is.
I've been looking at Aegis of the Sunbird as a good starting place for a new shield. I don't have much of an idea for belts and ranged weapons, but I figure those 3 areas in particular (as well as trinkets, rings, and necklace) should be replaced first.
Avoidance is parry + dodge + what the hover text shows when you put curse on your defense value + 5%. In general avoidance means you take no damage at all, so block is not included.
Your druid friend is pretty much right. With good group you shouldn't have trouble with the easier heroics, just remember to use CC to lessen strain on healer and to keep things under control.
If you're close at getting Shattered Sun Offensive to exalted that would be a good place. Other than that, check the pre-kara gear list, it should still be somewhere on this site. Cross check the items with your current gear and see where to biggest upgrades come from. For now health and defense would benefit you most as armor will come with the gear and avoidance isn't really that abundant until you get to T4 and beyond.
Got the S2 shield! This is by far the biggest single item upgrade, at around 30 extra stam (after enchant) and 2700 extra armor, I'm now almost at 15k armor and over 11k health. I still have a long way to go for getting more health, but I'm happy about getting near 15k armor.
The reason I'm using the Horseman's Blade is because it's approximately 30 dps higher than what I was using prior (which was some blue quest reward from a 68 quest or something), and I was fortunate enough for it to drop in a group where no one wanted it. Getting a faster weapon is on my agenda, but I'd rather get better armor, defense rating, and health before I focus on a faster weapon. It hits really hard and is great for Devastate
With Wrath so close, I'm going to hold off on getting the S2 shoulders and just focus on doing the heroic content I can do. I'm definitely going to work on getting my blacksmithing up to 375 before Wrath comes out so I will be able to raise it up to 450 and craft whatever tanking armor is available at 80.