Looking for stat "caps" advice

I have searched through a lot of threads here, and have read the guides posted (Much thanks to the people that took the time to write them!)

Basically, I played since launch all the way until I left the game in the middle of ICC back in wotlk. Real life took over. I was the guilds OT, and it was a highly successful guild that was one of the top on the server when I left (Since disbanded). I took tanking and my job very seriously, but so much has changed since I left roughly 3 years ago till now.

I am looking at tanking again, and have recently hit level 90 and have started my gear climb to be able to raid with some of my friends that are still playing from back in the day. I have found that, at least on my server, Warrior tanks (especially ones worth their salt) seem to be a dying breed. I want to do things right. Here is where my problem comes in.

I am looking for information on stat caps, specifically to be an effective tank what is the lowest rating should I have in specific areas to tank 5 man heroics, and where should I target to end up tanking 10 man heroics (eventually I will go on to 25 mans). I know, I know, 5 mans are face rolls, but like I wrote, the game is basically new to me now.

For instance;
I know hit till 7.5% Exp till 15%

But what is the base ammount of Mastery should I have?
Base ammount of parry (I understand the parry to dodge ratio)?
Ect...

Please understand I have an idea of how to prioritize the stats, and I do not want to make that the focus here.
Am I thinking too old school here? I just want to do the best I can, and if it means I have to ask these questions and look rediculous then so be it.

I can give an armory link if needed, but honestly, right now my gear sucks about as many balls as it can fit into it's mouth. I literally just hit 90 a few days ago, and have been gearing through crafting / AH / and just started running 5 mans.

You're thinking too old school. The way prot warriors work now is that they take less damage and have higher effective Shield Block or Shield Barrier (used interchangeably depending on boss mechanics) uptimes based on their rage generators, which are shield slam and revenge. Now... getting more parries/dodges does allow you to hit revenge more, and mastery gives you a a chance to get 10 rage on a block.... but the problem is that all of those are worthless if your hits aren't landing.

The way the rage gen calcs work out, if you're hit capped to 7.5% and EXP capped to 15%, then you're pretty much guaranteed to have enough rage to keep the maximum uptime on shield block, which is really what you're going for.

Now, if it's a boss mechanic where there's a lot of magic damage, then hit/exp become even more important because it's pretty much the only way to keep sbar up as much as possible. After that, go stam.

Mastery becomes pretty devalued as a prot warrior since if you need to be blocking something you probably have sblock up anyways, and more crit block helps but.... it's really not that big of a difference compared to missing a shield slam when you need it. You want to be sure to have your active mitigation up as much as possible in order to smooth the damage intake. Steady damage intake has never killed a tank unless his/her healers had already died. It's the spiky stuff that kills tanks, that's why you don't really worry about how much parry/dodge you have. You take what you can get from gear, but in general, this is the stat priority:

hit/exp >> stam = mastery (depending on fight mechanics) > dodge/parry

Honestly, I kinda like going the stam right just because boss fights right now have soooo much magic/unblockable damage that it really helps to have a big EHP pool.

Hope this helps, let us know if there's something else you need clarified.

Okay cool, thanks for the reply and putting it in laymans terms. Sorry if it seemed like a dumb question. I have been trying to rethink everything from the gameplay I used to know till now, and grisly old bastards like me tend to be hard headed when it comes to changed haha.

Yeah, the days of "400 defense rating or you no tank" are gone. Blizzard said they didn't find that kind of gearing to be compelling. Today, there are a lot of ways to skin the cat and the tanking theorycrafting is typically about the most "optimal" way to do it.