Language SHOULDN'T be a good reason for mergers. First off, everyone who lives in Europe know that German people especially are actually in general really good with foreign languages same as Nordic regions....many many german people speak pretty well english. Secondly, with today's technology, translators, etc....we can navigate through a game even if we don't speak the language. Besides, if merger, the mentor and guard teams will have to be bigger and I'm assuming mentors/guards will come from these servers as well so they can deal with their own players, etc...
Using language barrier as one of the reasons for not merging is a big load of dog poop....