Had this issue since 3.0

Happens A LOT when i am in an instance. I have tried-
-Restarting router
-Reinstalling FF
-Flushing DNS
-Changing DNS to google's DNS rather than ISP default
-forwarding ports
-disabling time sync as some people have said
-added an exception in windows firewall
-uninstalled my anti-virus software
-tried dx9 client and dx11 client
-tried using wtfast and pingzapper; it disconnects these too

Extremely Prominent since 3.05, unable to go into instances during peak time without disconnecting every 1-5 minutes with 90002
I can say for sure that it is FF due to the fact that i have a ping running to the NA server constantly and it does not drop any packets or fail to ping during these game disconnects, and during these disconnects other programs teamspeak, IRC, steam etc do not disconnect

I hope this can be fixed soon, more information about it brought to light or even a work-around figured out as its making the game impossible to play