You are not alone. Since 4.0.1 I have had problems being a tank.
My survivability on content I’ve run doesn’t seem to be an issue. Zel could speak more to that as she usually is healing me, but I definitely feel like I’m just as durable as before.
My problem has been on threat generation. I’ve always had some problem being an AoE tank. In wrath that was a weak area for warrior tanks. Some rose to the challenge without a problem, others had more stress on trash pulls than on boss pulls. Since the patch I’ve noticed that on boss fights threat seems to be more of an issue for me. Previously on a Patchwerk-style boss I’d take a quick lead on threat and just pull away the further the fight went on even against the best DPS in our guild. Now I can’t say that anymore, and it is frustrating. Anytime you are comfortable in a role and things change and you can’t do what you did before as well, it is a bit unsettling.
So tanks trying to find themselves in this new world order, take comfort in the voice of other tanks who are less confident than they were a month ago. And like anytime I don’t know how to do something in WoW I use Google Fucking Search. When I feel I’ve got my groove back I’ll come back with a flowchart or a description of my system to help. Until then, stay strong and keep on shield slamming.