Tier 1: Levels 10 through 18
Talents became a little bit more awkward when 4.0 came out. Instead of gaining a talent point every level, players now get one at level 10, one at level 11, and one every other level thereafter. It takes a little bit of getting used to and can feel a little wonky at first when you realize that there are some levels where you really don't feel like you are getting anything, but it becomes second nature after a while.
The first few tiers of balance can feel like you are making some pretty tough choices at first because we have a lot of great talents in the top tiers. In fact, you are eventually going to end up spending eight talent points into the first tier alone. Your first set of three points are relatively easy choices, though. At level 10, 11, and 13, you'll want to put those first three points into Starlight Wrath. Nothing beats permanently reducing the cast time of your two major nukes, and you'll be switching back and forth between Starfire and Wrath as early as level 10 for the Eclipse bonus. In these situations, having a faster Starfire is the cat's meow (or the owl-chicken's hoot, if you prefer).
Your second pair of points, gained at levels 15 and 17, should then go towards getting Nature's Grace, predominately for the same reason as above. Given the way that Nature's Grace has been reworked for Cataclysm, it now provides a much more predictable amount of haste that you can benefit from. Although the effect now has a 1-minute cooldown, it is reset every time you proc Eclipse, which should be slightly more frequently than the normal cooldown, even while leveling out in the world.
Nature's Majesty is a great talent, but I would honestly save it for later at this point in time -- you'll be getting it soon anyway, I promise.
Tier 2: Levels 19 through 28
Some people may call me crazy, but balance druids have to have one of the easiest leveling experiences out of all of the hybrid casters out there, and one of the main reasons for that is gained right at level 19 and 21. With the first two talent points that you can put into the second tier, you absolutely must pick up Balance of Power. The 2 percent increase in damage is a nice little perk, but the main feature here is the conversion of spirit into hit. Hit is a grossly undervalued stat for leveling and is excessively difficult to find at lower levels.
Leveling various alts since 4.0 was released, I've noticed that the dungeon finder loves to send players into to places that they are only just able to complete. The worst by far is getting Dire Maul: North at level 43, when all of the mobs are level 46. Throughout the world, you are constantly going to be fighting against targets that are higher level than you, and your chance to hit against these mobs is drastically reduced. Hit is a huge lifesaver in these situations, and as I said, hit is hard to come by. Spirit, on the other hand, is everywhere; and balance druids are one of the few DPS casters who get any benefit from spirit at all.
Once you hit level 23, it's time to go back and finish out Nature's Grace, and the two points you get at level 25 and 27 should be invested into Nature's Majesty. Genesis, you see, is a great talent, but it isn't a great leveling talent. Very few mobs you encounter while leveling are going to live long enough for the additional DoT duration to even matter, so the benefit from the talent is rather wasted. Genesis is more of a raiding or late game talent for when you are fighting mobs that are going to last a long while, which you shouldn't really encounter at this stage.
Moonglow is slightly more questionable than Genesis is. Mana is certainly a concern for balance druids -- especially at this stage when you don't have Euphoria and don't get Innervate until level 28. If you are running around in BoA gear, then your damage should be high enough -- and the mana return from the trinkets should be enough -- that mana will never be a concern for you. Without BoA gear, though, mana can be a bit more of an issue. If you don't have BoA gear, then you might want to get Moonglow instead of filling out Nature's Grace and picking up Nature's Majesty; just remember that your mana regeneration is going to improve significantly in only a few levels.
Tier 3: Levels 29 though 38
Another fantastic tier of talents for balance druids, and once again, you'll eventually want to pick up pretty much everything here. Your first talent point at level 29 should go into getting that one talent you'll either love or hate for the rest of your time as a balance druid: Moonkin Form
. Extra damage, extra haste, extra armor -- what's not to love?
Your next point at level 31 should go into picking up Euphoria for the additional mana regeneration, which you're probably begging for at this point. The points after Euphoria become a little more tricky.
The second point into Euphoria does not increase the mana returned from getting Eclipse; it only increases the chance for proccing additional Solar or Lunar Power. While great, it isn't that important for leveling. Between levels 33 and 37, you'll gain three talent points. Two of those points should go into picking up Shooting Stars
. That last point is a little more questionable; it can either go into filling out Euphoria or into picking up Typhoon
. My vote goes towards Typhoon, but the choice is up to you.
I will say this for you wonderful new balance druids out there. For the love of whatever you believe in, do not use Typhoon at the start of a trash pull in a dungeon. This seriously can piss off your tanks, especially in a group of casters in which positioning is already painfully difficult. Typhoon is a great spell for getting things off of you. Use it defensively; please do not use it when you feel like sending out a large wave of annoying. Tier 4: Levels 39 through 48
The first weak tier in the balance tree, at least for leveling. This is the time when you're are going to find yourself going back and picking up the talents you've previously skipped in favor of something else. Your first talent point should go into picking up Solar Beam
, but the remaining four points should be used to pick up anything you previously passed over.
If you are starting to feel that you need additional mana regeneration at this point, then go back and pick up Moonglow. If you already have Moonglow, then fill out Nature's Grace and Nature's Majesty. If you aren't having mana issues and already got your fill of nature, then fill out Genesis and Euphoria.