Unplayable lag/disconnects when in party

I've been playing the game for ~10 months now and have never had any major issues with lag or latency. I've had the occasional disconnect here and there and a little bit of desynch but nothing serious. I've been away from the game for 2 weeks or so and now that I have returned I am finding that I can't group at all due to constant disconnects and latency. I suspect these problems are due to grouping with players in the EU gateway. I ran pingplotter with the US gateway and didn't see anything weird, but when I ran pingplotter to the EU gateway I got this atrocity:



Anything I can do on my end or do I have to resign myself to avoiding grouping? That'd be pretty awful as it's pretty much impossible to level masters without grouping...