My experiences are actually on both NA and EU servers, though they seem to be worse on EU servers (I only duel before strat matches)
I can totally understand people needing to train with weapons that happen to have polestagger, or knockdown, and/or crushthrough, but there are a handful of players who just duel to win at any cost, many of whom do not actually do very well on Battle/Siege (where there's an actual team to support, see: Chambering) and I'm trying to understand WHY.
And again I am not really bothered by this. After a few rounds of "Whoops, I got hit a single time, guess I've got to just stand here while he hits me five more times!" I get the message and stop dueling those people, though they often still try to duel me. As I said I will basically just duel anybody, you fight any kind of opponent on the other servers, but it seems a lot of people use dirty tactics which are only regularly encountered on duel servers.