I (and many many others) have dealt with lag of various forms in DDO for-elfin-ever.
[TLR version. A cable splitter used with high speed cable internet to split incoming signal was causing 95% of the game stopping lag I had playing DDO.]
I am not talking about UMD lag or slow video rendering.
I am talking about your character just stops, can't move, cast, tumble or do anything.
I get no green, yellow or red box indicating chat server loss.
Speed test yields very favorable results when ran.
I have a 2 yo PC with lotsa RAM and good Video Card.
The character just stops (but buffs continue counting down and mobs continue chewing on you).
My GF and her son (age 8) recently moved in. With him watching netflix on the Wii, both her and I experienced even worse lag. She continually got booted from COD BO2 matches, DDO was still laggy as H AND I kept getting booted from the GW2 servers too (spent $60 on a great game I like vs $200 for 2 VIP DDO subs this year, ftp ftw).
After calling Comcast I found that the Cable Splitter splitting the incoming Cable line to goto the cable modem and DVR was the culprit.
With the Cable line going directly to the Cable Modem then to the Wireless router I very rarely get kicked from GW2 and about 95% of the game stopping lag I experience in DDO is gone.
Hope it helps.