Half of the problem with aoe threat is the dps attacking 15 different targets and expecting the jugg to hold them all it's not done. Sins/PT's have a better snap aoe aggro gain where jugg's smash and aoe taunt are minimal at best. I typically don't have too much trouble holding adds in nightmare/hard OP's being the only tank for most of it just have dps hold off i use TS, smash, intimidating roar, smash again and probably sweeping strikes. if they start to pull away use chilling scream. Some of this lack of better aoe threat is on the dev's the other half is the players.