Many dps are just too bad to manage their aggro. On my sent I open with around 6-7k dps and after the first rotation I just use my aggro reduce and then I use it on CD. Never pulling aggro.
use 2 ap proc relics and you're good. if your cauterize isnt up reset it with merciless/slash and zen right when u apply the 3rd stack (u can apply 3rd stack with cauterize btw)
Never loosing aggro on a vanguard tank, unless a few misses occur. In most random raids I don't even give guard to the dps, even if he asks for. Most can't manage to pull aggro anyways.
BIS relics depend on the encounter!
For NiM Dread Guards I am way better wtih 2x DMG Proc because of lots of movement(ap procing when you're not goign to attack the next seconds)
For most encounters I am pretty good with kinetic tempest + ap proc. I tried on the dummy uw ap+obroan ap but it did less over 5 parses than 72dmg+obroan ap