First yes Guild Wars 2 is using Glicko-2 but a little changed, first it use a min and max violate and min max Deviation that means, this littel trick has his limits. Beside that we have to problem with not many players are able to control a match in that sens to effectiv "farm" Deviation, out for that simple reason u are not alone. And now the truth there is nothing better, many Ranking Systeme has similar or even the same issuse.
Here is the wiki Link for the GW2 MMR System: https://wiki.guildwars2.com/wiki/PvP_Matchmaking_Algorithm