Okay, so there have been threads, there have been reports, there haven't been many answers. So, lets just sum up all the crazy bugs, lags, basically everything that is wrong following the Dark Brotherhood Patch, with visual proof, just so that everyone realizes the extent of the damage.
@ZOS_JessicaFolsom please forward it to the appropriate authorities yet another time. Seriously, even a message such as "we noted these issues, and will do our best to fix them on Monday or whenever the next patch will be" would be nice

I mean the messed up ulti cost is an even bigger nerf to sorcs. We have 3 useful passives, and one of them ain't working. See the problem?
Here, enjoy.
Slowly losing faith in this game, the player base, and humanity in general,
Kasa.
1/ No ultimate cost reduction abilities/passives/weapon sets (see, vampire skills, sorc passives, potentates set). Video below illustrates it with Dawnbreaker, supposedly costing 85 ultis with the Power stone passive but not launching until 100 ultis.
https://www.youtube.com/watch?v=pJFqJonwF8w2/ Vanity pets active in Cyrodiil. Nuff said, they already cause lag and delay in trials, just imagine the damage it could do to the already abysmal performance in Cyro


3/ Inexistant sound - both in PvP and PvE
Here, notice in PVE the significant FPS drop at boss fights, which makes it almost impossible to see one-shotting mechanics. This didn't happen inb4 the patch, or at least to a tolerable extent.
https://www.youtube.com/watch?v=yuFk9zveOfg&feature=youtu.be4/ Nova visual effects - "aaaah, my eyes, it burns!"
https://www.youtube.com/watch?v=PcF2F477Xlg&feature=youtu.be
5/ Poisons being wasted on freaking stamina-based heals. See in the video below, poison charges deplete when I use vigor.
https://www.youtube.com/watch?v=WY0UzPzuLdU&feature=youtu.be
I've got a lot more, which I'll upload as soon as I have the willingness/time.
Notable bugs:
_Weapon swapping - you get stuck holding your bow like a 2h sword, resto staff as dual-wield, and vice versa...
_PVP: getting hit by invisible attacks (mostly meteors) due to the sound and environment not rendering when you encounter more than 10 people in one spot.
_Attack clipping. Okay, combat animation priotization. Seems like a harmless thing. Well, it ruined combat overall. When before you could weave light attacks with your wrecking blows, now, these light attacks do not launch. Same goes for PVE. And that's without mentioning all the clipping.
If anyone has any other things to report, which I'm sure I've missed, feel free to add it. But hey, DLC came out a day and a half ago, so I didn't have time to get footage of everything wrong with this game xD
Don't forget, the more footage you get, the more you QQ and overall voice your disappointment in a very vocal manner to anyone who bothers listening, the sooner it might get fixed.