Like the mobs in the Pavilion, almost all the mobs in the LS (not the new zone, the actual LS instances) do not count as kills and thus do not trigger kill effect sigils, food, or traits (complete list here: http://wiki.guildwars2.com/wiki/Kill_effect).
I can understand not wanting the mobs to give exp as anti-farming/grinding measures, but can we please get a solution that doesn’t break parts of the game mechanic?