BTW I dislike the tight armour as well. I thought the Oblivion design was good, but i hate the skyrim one ...
I keep hearing this, but I don't think there was a http://chorrol.com/files/141/ob_concept11B.jpg http://images3.wikia.nocookie.net/__cb20111028154345/elderscrolls/images/8/84/Dark_Brotherhood_Female_Armor.jpg between the two. Both armors look remarkably the same, especially compared to other armors that made their way from Oblivion to Skyrim. I get that its "tight", but it isn't any tighter than the Oblivion one, or even the http://bestgamewallpapers.com/files/elder-scrolls-3-morrowind/dark-brotherhood.jpg
RavenBlade, as far as politics goes, the Dark Brotherhood would look after itself if need be. Any organization would. And while they wouldn't take their own initiative in politics, they have, from assassinating the Emperor in Skyrim to attempting to assassinate the Nerevarine, they've always been involved in politics, though they've always taken the position of a neutral party to implement the will of either (and sometimes both) side(s). Its the best way to keep the business going.
As it has been made clear in previous titles, the Dark Brotherhood used the fear of retaliation to make sure their organization continues to survive and prosper. But, as any organization that relies on intimidation and fear has probably learned at some point, these methods are a double-edged sword and often inspire retaliation that far exceeds the intimidator's original levels of brutality and violence. The Dark Brotherhood really hasn't seen much of this itself, as far as we know, but when faced with such a retaliatory situation, its hard to believe they wouldn't move to defend themselves.
Also, yeah, neither the Empire nor the Thalmor has much use for them. The Empire has the Oculatus, which is full of loyal, order-abiding members (not chaotic sociopaths) willing to assassinate and die for their Emperor. The Thalmor probably has their own organization of spies and whatnot, but they'd probably rather die than ever work with the Dark Brotherhood. The Thalmor hates Sithis and everything he represents. In fact, when I first heard through the forums here that the Dark Brotherhood sanctuary in Bravil was destroyed, I thought it was the Thalmor that destroyed it during the time that they held Bravil during the Great War. Perhaps the Empire doesn't have the drive to eliminate the Dark Brotherhood, but the Thalmor certainly does. Though I suppose they're busy with more important things, at the moment.