Just for kicks:

Last night we went to Amdapor with the guild. At one point, i kept launching spells and everything was frozen on my side, mob not moving, mana not going down, etc... I was at the same time on TS with the mates. They told me the mobs died. So since I could, I started launching blizzards 2 in chains... and guess what:
* They could see them and they could even tell me how far was my mana or my life but I could not.
* And they could tell when I was casting and when I was not pretty much in real time.
* The server ended up DCing me though it could actually receive information from me.

So, the problem does not seem to be, at least in my case from ME to SE, but from SE to ME. Which brings me back to a problem on SE's end. Maybe not enough outgoing throughput ? OR it means my firewall and box in a way or other started dropping SE incoming packets. Which I doubt, but I will ask my ISP nonetheless for info. They don't throttle.

Also, the same thing kinda happened with the chat server. I could not see the discussion, but I could play the game pretty well. Did not think of trying to send a message though.