I'm noticing anyone with swarm out is basically like walking directly up to a meat grinder and jumping in. I wish I could say it was my own subpar ability at PvP but as a troller I'm lasting longer against tanks than anyone hanging out with bees.
I was running some arenas with my league 1 member if the opposite team had swarm was able to take us all out in seconds. It seems to ignore the toughness of pvp gear making you basically naked against it. It was doing it once before around the time home turf was released.
Problem may be its an ongoing dot (as I understand it). You try to attack it, its owner attacks you, you attack owner and swarm attacks you. Vicious cycle
Seems to be working as posted .. ran a 1v1 with a nature healer with healer gear .. and his swarm just almost melted me . Granted I was ice but was dps gear/dps spec and he had role advantage over me ; but he was barely full 89 and the swarm was ticking up damage like my gear did not even exist.
It's not ignoring toughness, and you can test it in a minute by dueling someone. It's just really strong.