So maybe this is just something i have to deal with because I have a bad wifi connection... but often I will go LD while in the process of loading a zone.

After this happens, when I try to login I will get "you are not allowed to dual login...etc" message.

I'm guessing there is some time out that has to expire as the game must "think" I am still logged in. Eventually after a few minutes I can log in again.

However this delay can be quite annoying and sometimes deadly. Is there any way to get around this or can that timeout value be lowered?

You need to remain patient and wait for your character to finally disconnect from the game. It's intentional, both on Uthgard and Live, as it limits a Players' ability to abusively crash their client to leave a messy situations.

Players in VoiceChat together can inform you when your character finally leaves the game to know when you may log back in.