We've been at a 30% buff for a while now and still no guilds have killed heroic Lich King on 10-player without having 25-player gear. It's not time to throw in the towel yet, but at this point I feel like I can say that 10-player raids in Wrath were a great but failed attempt at providing an alternative for players who prefer the smaller raid size.
There is a good chance that Blizzard developers actually agree with a great deal of the criticisms I have to 10-player raiding in Wrath. They are, after all, significantly changing the paradigm for Cataclysm to eliminate the gear gap and prevent people from running raids of both sizes every week.
It has been fairly clear from the beginning that designers were designing 25-player bosses, and then just nerfing some numbers to get the 10-player version. Sartharion plus three drakes was our early proof of this. With the limited staff available to handle the multiple drakes at the same time, the 10-player version was widely recognized as being harder, person for person and gear for gear than the 25-player version. Were it not for the viability of rushes, that would still remain a fight that a relatively small number of players had beaten even with today's gear. In order to beat that fight we were forced to gear up in 25-player content. To my knowledge no one ever won in 10-player gear.
In Ulduar encounter design got better, but the 10-player version of encounters had several glaring problems. Often the solution to a 10-player predicament was to remove a troublesome mechanic altogether. Impacts of other mechanics on groups of different sizes, such as the mind control ability of Guardians of Yogg-Saron weren't even considered.
Ulduar was still a masterpiece, and it was great that they reduced the gap between 10-player and 25-player gear, but ToC brought that gap back. Moreover, the ToC trinkets were itemized so differently that the 25-player versions were great and the 10-player versions were universally terrible. While 25-player players were using on 245 and one 258 trinket, most 10-player players were using one 219 and one 200 trinket, because even the 245 10-player trinket wasn't worth equipping.
The trinket problems continued into ICC. With only one new trinket for each type, and those trinkets being unique between the heroic and non-heroic version, 10-player raiders got to upgrade only one trinket slot, while 25-player raiders got to upgrade both, often with very substantial upgrades. 25-player raiders also got Shadowmourne and are still benefiting from Val'anyr. 10-player raiders, on the other hand, can find noticeable holes in the gear offered to them, such as (at least at the time of release) there being no wand without hit in ICC. In ToC 10-player raiders could only upgrade their 219 cloaks (or 226 cloaks from 25-player Kel'Thuzad who we needed to kill to beat Sarth +3) completing a successful tribute run. No other cloaks were in the dungeon at all.
All the while 10-player guilds have to contend with a great deal of difficulty in recruiting because of the perception (and frankly, the reality) that they are second class raiding guilds. Attempts to recruit the best players were hamstrung from the beginning because most players would rather play at the difficulty level that gives the best loot. With 25-player normal giving the same loot at 10-player heroic, which is comparatively very hard, there is little incentive to join a guild dedicated to 10-player raiding.
25-player guilds got to trivialize 10-player content by overgearing it and having lots of extra practice at it. The limited attempts system ensured that they would take that time practicing as well. Probably more importantly, a 25-player guild attempting to get 10-player kills can bring in extreme raid compositions that are ideal for the encounter. 10-player guilds may only have one member of any given class, or none at all. 25-player guilds will almost always have two of each class and often three. If one class shines on a particular encounter, they will always be able to bring them. Imagine the poor 10-player guild who makes it all the way to heroic LK without a priest and then finds themselves at a desperate disadvantage due to having no shields for Infest.
All of this, however, brings me back to the Lich King. I don't know whether my guild will beat him or not. It may be we just need a hundred or two more attempts to get the fight down, but it may be that we are simply not up to the challenge. I don't doubt that this is our fault; there are probably many different groups of 10 people in the world who could beat the lich king on heroic with our characters. But none of them actually play 10-player exclusively. 10-player heroic Lich King has been, up to this point, nothing but a source of higher level weapons for guilds working on 25-player Lich King. The next few months will determine whether he ever becomes anything more than that.
Part of it is that I'm just disappointed that we haven't been able to win. Part of it is that I wish I was better at playing and I could stop making mistakes that are costing us attempts. But there is definitely a part of me that feels like being 14th in the world should mean we are good enough to take things down, and at the very least 1st in the world should.
Ultimately, for 10-player raiders, the final boss of the expansion was balanced to be out of reach. He is not out of reach for a theoretical raid, but he is out of reach for the people who are actually playing the game. I hope that someone can prove me wrong before 4.0 hits or he is nerfed (and I would love it if that someone is me) but at this point I would probably be willing to put even money against it.