What is the AoE cap for balance druids? Is it the same for Starfall and Hurricane? Nothing in the Theorycraft think tank article or from the WotLK balance threads.

It was changed in the beta, and Blizzard said it's not something you should expect to run into in normal play.

I haven't run Hyjal recently to see if it shows up there. It didn't seem to appear during the spider wing of Naxx in beta.

For mages the cap it's universally 25k damage per second cast time.
So, Flamestrike (3s cast) has a 75k cap, Blizzard has a 25k per wave, instant spells count as 1.5s as always and have a 37.5k cap.

I doubt it's different for other classes since this seems pretty universal. The numbers are for level 80.

Whats the best feral leveling talent build?
The goal would be to get the best balance between kitty soloing dps and still being able to tank an occational instance without having to respec.
My current spec is this (and i know its not good!):
World of Warcraft Europe -> Talents

EDIT:
Could this maybe be viable?
World of Warcraft Europe -> Talents

They both aren't to bad, but if you're going to get Omen of Clarity, you really want to grab Naturalist on the way.

For tanking, I chose to just take Thick Hide and Protector of the Pack. For the first instances it really is enough, even overkill if you are at least halfway geared...

Primal Precision is, with the lower caps on hit/exp against same level mobs, not really useful, at least in my opinion. That changes once you get into raids, but that's not the topic.

I'm 72 now, and currently this is my spec. I'm going to max King of the Jungle and then imp. Mangle.

I agree on the hit/exp point, but the 80% energy refund on missed finishers is worth it to me. Just my 2c.

Once you are capped with exp and hit for the mob you are attacking that becomes a moot point because you won't be missing/dodged/parried.

I don't have hard numbers for 70, but when I got called into Hyjal for Kaz/Az, I was doing 6-7k on trash waves (frost mage), as was our Boomkin. That also jibes with numbers I was getting when I had a tank for scourge invasion clearing. We aren't even in t6, so maybe somebody in sunwell gear would hit the cap, but I definitely did not.

I have leveling builds up on my US druid leveling guide:

World of Warcraft - English (NA) Forums -> NEW 3.0.3: Feral & Balance leveling guide

I've been updating on a fairly regular basis, based on player feedback and more experience playing with the talents. I have specs up for both balance and feral, and I played around with both specs during Alpha/Beta testing. I'm estimating that the guide will undergo significant changes during the week of Thanksgiving (when I get a break from my graduate school classes), but the basics are there.

There really isn't just one spec that you can have for leveling. There is a lot of flexibility. There are, however, talents that I like a lot better than others. The real thing that becomes a personal decision is when to pick up all the resto points that you need in either a feral or balance build.

I tried various feral builds on beta, but I ultimately decided to go with this. Talent Calculator - World of Warcraft At 71 I put a point into berserk and then started filling out Natural Shapeshifter towards Master Shapeshifter. My general plan is to Mangle, Rake, Mangle, Mangle and Ferocious Bite as soon as I hit 4 cps. Rend and Tear - Spell - World of Warcraft is stunningly good for leveling with Rake and Ferocious Bite.

I've found it better to rake first, as the initial damage of rake is strangely not affected by mangle, the bleed doesn't start for another 3 seconds and it means getting the DOT portion out earlier so you can maybe get 2 ticks before FBing.

I would go with this: Talent Calculator - World of Warcraft

I don't find Shred useful at all for leveling, and rage for lacerate is hardly an issue, so FA becomes the next best option as far as catform goes. At 71 take Berserk, then fill out RnT and then Shapeshifter

With the changes in WotLK, is there ever a point where Mangle will out-pace Shred?

I have DrDamage installed and I noticed the following:

With 5/5 in R/T, both pounce and mangle debuffs on my target, and the [Everbloom Idol] I'm getting around 48.X DPE on Shred.
My Mangle was getting 44.X DPE.

I'm still testing this but it seems like with Mangle's lower energy cost, combined with [Idol of Terror], it's not worth putting Shred in my rotation.

As balance should i be spamming wrath or starfire after applying dots, or both based on eclipse?

You can find plenty of info in the wrath balance theorycraft thread - Try searching the last 10pages or so.