I'm just glad I'm not the only one. Too many fans (lore buffs included) criticize every game Bethesda makes. Oblivion kind of deserved it with Nu Cyrod, but I can tell Bethesda has been trying to stay consistent with lore in Skyrim, even if they haven't been as upfront with it. But in Dawnguard, they really tried to show more open regard for the lore. We got to meet a freaking moth priest for goodness sakes!
An old lore buff was saying, that with each new game, we are realizing how much we truly don't know about Tamriel, and I think this is true.
It's very true.
While somethings in the Lore are quite specific, other things (like Vampirism and the number and variety of Clans) are more generalized and gives the devs more opportunities to flesh them out and rework them without breaking their own Canon.
If they wanted to, I'd even be perfectly happy with a retcon to make it all fit, and being that they're the devs, they're allowed to do that if they should so choose. It's worked very well with Halo and StarWars, and those two universe's have just as much Lore behind them as the Elder Scrolls do.
In Skyrim, they've really fleshed out the Lore by a great deal, and even added a previously secretive but very powerful Clan who were/are created by Molag Bal himself, pass on their Gift to others, and thus grow stronger. No where in the Lore does it specifically say that Lamae is a Volkihar. Nowhere.
It simply states that she is the
First Vampire. It very well could be that Lamae is a Vampire Lord, and that the Volkihar (while still extremely powerful Vampires) are simply weaker cousins to the Vampire Lord.
They've fleshed out the story of the Falmer, so they could be in more games'expansions/DLC at later dates due to finding an unaltered Falmer. He also hints that he strongly believes that there are pockets of other unaltered Falmer hiding throughout Nirn, so he plans on finding them over time and helping the Betrayed Falmer to try and reclaim their former Nobility and Dignity.
The only Lore that's being "corrupted" is people's interpretation of said Lore. People have this vision of the way the Lore is "supposed to be" and are unwilling to acknowledge it more generalized nature.
Dawnguard and Skyrim have further fleshed out and codified the Lore, not betrayed/destroyed it.