Complaint 1: Balance druids do not scale as well as other classes!
There is hint of truth to this claim, but overall it is not entirely correct.
Balance druids currently do have some serious scaling issues, however much of those issues are a result of the way in which gear has scaled in of itself and are not entirely a fault of the balance spec itself. The only real exception to this is Nature's Grace, which is a monstrosity that never should have been carried over to Wrath of the Lich King to begin with. Nature's Grace is the direct cause of what people will point to as our first scaling issue; the Haste soft cap on Wrath.
Wrath has never really been a PvE spell, and for this expansion Blizzard went out on a very thin limb to try and make it PvE viable. Eclipse, much as people will state otherwise, is not the direct reason we use Wrath in PvE. Most of it had to do with the way that buffs changed within Wrath, most notably the increased Spell Damage buff which was changed from being school specific, with no Nature school option, to being applied to all spell damage. These changes were not entirely complete though because Blizzard missed the core of why Wrath was no used in PvE - Nature's Grace. Wrath has always held a higher damage yield than Starfire due to the Starlight Wrath talent and even way back when the Starfire Glyph indefinitely increased Moonfire's duration, Wrath still had a place within our rotations because, anytime there was time enough to cast Wrath without losing Moonfire, it was a DPS gain. What Wrath lacks in its scaling from Haste, it more than makes up for in its scaling from Crit and Spell Power. Wrath scales amazingly well with Spell Power, again mostly due to the Starlight Wrath talent. Although stacking Spell Power is not very plausible, there aren't really many ways you can get a significant amount more Spell Power than another class of equal gearing, Spell Power is one of the fastest increasing stats you will see. Not only will our own Spell Power scale higher with gear, but if you raid with a Demonology Warlock, your Spell Power will scale with theirs as well.
The second scaling point that comes up is Starfire's scaling with Crit. During a Lunar Eclipse, you need to reach approximately 60% Crit with Starfire in order to reach 100%, this is, of course, not accounting for additional raid buffs. Once all the buffs and debuffs are factored in, a balance druid should have approximately a 65% chance to Crit with Starfire during a Lunar Eclipse- meaning that gear needs to account for 35% additional Crit. For all the flak that Intellect takes as being a poor stat, it will actually generally end up accounting for roughly 10 - 11% Crit once you are fully raid buffed and in Moonkin Form. This means that your actual Critical Strike Rating needs to account for around 25 - 24%.
Now, it takes 45.91 Critical Strike Rating to make 1%, therefore a balance druid is going to need around 1102 - 1147 Critical Strike Rating on their gear in order to reach the Lunar Crit cap. Our Idol is going to be a very major source of this, accounting for 220. That leaves a druid needing, at the lowest estimate, 882 Critical Strike Rating on the rest of their gear.
Most balance druids raiding ICC at this point should already have over that amount, but how much is it actually going to increase? It all depends on how you choose to gear yourself. There is no doubt that Reign of the Dead is our BiS trinket, both versions for that matter. Using both of those trinkets, a balance druid can predict that their Critical Strike Rating it going to be around 1047. Without them, it should only increase to 1178. I would imagine that more druids are going to have the 1178 option than the 1047 one, this means that, during a Lunar Eclipse, 291 of your Critical Strike Rating is, essentially, 'worthless.'
That accounts for 6% Crit that isn't of much use for a section of your rotation, but, there is one important detail that was glossed over. Since raid bosses are 3 levels higher than us, you do not need 100% Crit chance, you actually need around 103%. So, at the highest level of gearing, a balance druid is going to miss out on approximately 3%, maybe a little more, Crit from their gear. This honestly isn't a major scaling concern.
Now, this is not to say that the additional Critical Strike Chance we are gaining is all sunshine and roses. Our abuse of the stat does have some drawbacks in terms of scaling depression, but the fault in this should be placed where the fault lies, and that is not in the mechanics of a Lunar Eclipse and not within the Lunar Crit Cap. There are lots of classes that have similar, and higher, base critical strikes chances than we do. It is less a matter that the Crit from our gear is holding less scalar value and more an issue that the bonus from a Lunar Eclipse proc holds less of a value.
Complaint 2: Eclipse!
Ahh, the talent that every balance druid loves to hate. The talent that has been the single bane of our existence since Alpha. The talent that many balance druids would like to see tortured in unspeakably horrific ways until it is finally laid to rest. In all honesty, I find the hype against Eclipse to be grossly misplaced. There are issues with this particular talent to be sure, and I am by no means a strong advocate for its continued state, but the beef that many players have with this talent is blown way out of proportion.
Graylo recent had an article going more indepth on the issues surrounding Eclipse, but there are still some things that need glossing over. To start with, I really want to stress these important things: Eclipse used to be far too RNG heavy, Eclipse used to be far too cumbersome, Eclipse used to be a complete failure of a mechanic, but now it has found a note of redemption.
Eclipse is based around Critical Strikes which places control of the mechanic beyond a player's reach, and that is the real frustration of many players. The reality is, gear inflation has made Eclipse so viable that it isn't funny any more, really, it isn't. The complaints of bad Crit RNG held weight back in Naxx and even slightly into ToC, but they simply don't have much of a place in a word where balance druids are literally running around with neigh 70% Critical Strike rates. Yes there are still probably going to be a few times where this talent frustrates you - I cannot even begin to recount the times where I've needed that added burst damage from Eclipse but it just wasn't there - but throughout an encounter, it really doesn't make a difference.
Honestly, it doesn't. Within a standardized 5 minute encounter, the minor nuances of Eclipse RNG simply do not have a major impact within our DPS potential. Going 5 seconds additional seconds between your expected Eclipse proc rate will equalize out to only be a loss of a spare 100's of DPS here and there. While that may certainly seem like it could add up within an encounter, and it can, it is generally going to be off set by those times when Eclipse procs earlier than expected. Remember that it is generally assumed it is going to take 2 Starfires or 3 Wrath's minimum to proc Eclipse, and there are definitely times when it is going to proc earlier than that.
Complaint 3: Movement!
Balance druids are not a very mobile DPS class, to this I agree, then again, I don't really think there is such as thing as a mobile caster. Even Affliction Warlocks and Shadow Priests have a very significant portion of their DPS accounted for by spells such as Shadow Bolt and Mindflay. While such classes may not lose as much as we do when they are forced to move, every caster is hurt by movement.
Movement is merely the reality of encounter mechanics, there are no ways around that. You are going to have to move, period. It is going to happen. There may be a few encounters where you do not have to move, but, as a general rule, always assume that you are going to have to move during an encounter, because you almost always will.
Movement is bad, but it isn't as bad as people are leading everyone to believe. Remember back to Eclipse, we don't lose that much DPS if it is going to take us a little bit longer to get that next proc off, and smart game play can usually off-set a good portion of that loss.