I've noticed that on single target, tank and spank type fights, that my campaign geared Vanguard isn't holding threat off of equally geared DPS (Command and Sentinel in this case). I used to be able to maintain threat in these situations just using my most efficient threat rotation, but several times, I found I had to taunt mobs off of both (I was guarding the sentinel at the time).

I wouldn't go so far as to suggest the class is broken, but I definitely feel like my threat generation is compromised to a degree.

Are there any math nerds out there to sit through a few parses for us

My threat generation seems pretty low and I'm constantly wrestling against dps for aggro. I can do it, but usually it's pretty hard work, even single target boss fights unless I use my taunts on every cd.

Healing wise my healers love it, I don't take a lot of damage unless it's a pretty nasty pull. I also have a (sage) healer and I believe I'm comparable to the rest of the guild tanks for taking damage, certainly we don't have all the def cd's the others have, but I think that side is more or less ok.

Damage output has definitely suffered imo, but yeah the threat output is my biggest concern. I don't see a lot of posts or QQ about it tho, very strange... math nerds to the rescue?

I run into no threat issues on my PT tank. I tell my DPS to go full throttle from the start.

Jet Charge (or whatever you VG's call it, the gap closer) > Stock Strike > Shoulder Cannon during GCD > HIB > Shoulder Cannon during GCD > Energy Blast (if it's up) > Shoulder Cannon GCD > TAUNT > Ion Pulse > Shoulder Cannon GCD > Use your free Flame Sweeps/Explosive Surges or Ion Cannon/Flamethrower

If your Ion Cell doesn't proc from your Stockstrike (it got resisted), prepare to taunt immediately after Shoulder Cannon, and then use your AoE taunt next.

I run with well-geared Mara's, Merc's, and Snipers in my raids. No one pulls off me unless I derp around in the beginning and not use my taunts in my opening rotation correctly.

EDIT: And no, our threat generation did not get nerfed. The 5% damage reduction in Ion Cell isn't that bad. What you guys are experiencing is the new resist mechanics. Before 2.0, the majority (or all) of a PT/VG's threat came from tech abilities that could never be resisted/missed/whatever. Well, now they can be, which is why all DPS classes have to stack accuracy to 100/110%. So in the past, you very rarely had to use your taunts to maximize your threat in the opening of the fight, but now you have to. I got used to doing it on my Jug in pre-2.0, so it's not a big deal. Hell, if I don't use my taunts appropriately in my opening rotation on my Sin tank, someone can pull off me if my Wither/Discharge/Shock gets resisted.