Massive lag upon boss death

I party up with someone ready to do the same boss I'm working towards. Network is rock-solid at 80ms, not amazing but sufficient. Fight the boss for ~2 mins (brutus) anywhere up to 5 min (oversoul). No problems whatsoever.

Now at the moment where the boss is going to die, I get a massive lag right before he falls over. Not a loading stutter. I can move my character, I can attack, but I've lagged out completely.

This continues for some time, and I end up disconnecting. In two cases prevented me from taking the zone portal to the next area, in one case almost got me killed - lag continued following the boss kill even though I didn't D/C; didn't want to lose the waypoint in the next area, so I ran through to get it. Continued to lag and a pull disconnected me.

I don't have amazing internet, but it's not terrible either. Line quality in the area allows me standard 1.5 mbit DSL. It's pretty stable, so this would be a very strange coincidence for my internet to choose the moment of a boss death 3 times in a row to completely bog down and fail.

It happened to me a total of three times today, and I don't have enough info to even make a guess of what's happening. Either I'm just extremely unlucky, and my internet has chosen 3 very consistent moments to crap out, or there is some glitch with today's patch saturating my bandwidth at times. I haven't had a chance to go back to default to test it, busy logging off when this occurs to prevent a death. I'm playing the HC race atm.

Could be a denial of service too, I suppose. Maybe someone wants to see me dead :b. I do hope client.exe doesn't have any behavior that'd allow a party member to find my IP.