.... there is no best server.
other then behemoth :P
but.... all NA/EU servers are in Canada Ontario
instance lag?? cant be helped duty finder mixes worlds for it... so its more of a SE issue
if its in world lag it could be ur connection?
are u forwarding your ports?
do u have other ppl useing the internet when u are player?
both of the abouve will make u lag big time in and out of an instance