OK man. I've the VERY same problem as yours. Here's the thing I did and here's the findings I got.
Like what you said, I've the same prob as you as well. It appeared out of nowhere at all, frankly it's annoying me so much, I stopped raiding for the last four months. JUST WHEN THEY FRIGGING MADE INTO MH/BT!
... fuggers..

Anyway.

Computer/UI/Addon/whatever shits.
No, it's not your computer. I believe you've done all the necessary steps in doing that one. I've gone to the extent of changing my RAM, display unit and believe it or not, changed my OS as well. Nothing, and I mean NOTHING helped.

You get DC during heavy fights. I believe your com can take in fair amount of data, sync, but during large scale pve content, there's so much data floating around, it's simply near impossible to do it. Why? Spikes.
Yeah, connection spikes. Your UI/addon furiously try to keep up with the rest of the raid, while you're getting NO connection from the server, then after a good 2~5 seconds, you get lagged out, you'll know when it happens. You log in back again, and being in mid fight, you'll get DC AGAIN, cause your UI/addon syncs with everyone else again and it's simply not fast enough. It's bullshit, I feel you on that one.

The only thing that helped for me is rewiring the home's phoneline. Yes, I'm not kidding. I now have a direct line from the phone jack outside of the house straight in. That helped the spike bits. Also, getting the right IP for it helps a lot too. 218.111.*.* works for me now. 600~700ms, I don't quite care, as long as I don't get spikes, and I dont' get DC.

It's extremely frustrating. But yeah, it lies with your connection/line. Not your computer like the rest claims. Keep on finding the root of the prob man. Good luck!

Not the way they decribed it. Lag spikes can't be helped. Even when disabled it still DOES causes the dc. Too much info such as damage and shit still goes thru. I've gone thru the extent of turning off damage reports down in the options, and no, I still get DC'ed.
No external UI, no external addons, no damage numbers.

Makes sense?

I began with telling the OP that I suffer the EXACT same issue he did, and I said here's what I did and discover along the way. The post was directed to OP. Not your replies, wherever that might be.

Re-read the post please.







You seem to just choose what you wanna read and understand what you choose to understand... or perhaps my english writing's not up to standard these days.

I'm at a loss for words, ain't gonna post further. Will let OP read it, and take the argument elsewhere. Ain't got nothing to do with this thread further more.