With what we have seen on EU Centrals Midgard I believe it should be done on all servers since AGS are not actively filling servers with merges and most are still at low populations not even peaking at 500 players.
I believe Tir Na Nog would be a good second Midgard since it has strong PvP, decent 650 peak players and good competition from all sides.
Shout some more servers and give thoughts.