Straight after Summer Festivals, there is now special event in GW2: Champion Rush. Champions are harder landscape mobs for groups. There is quite many these kinds of bosses around, and this event only counts so called "Core Tyria" bosses, which you can access without paying anything. The thing is: there is now lots, lots of people in low level maps, so if you were thinking of making a toon, or if you have one, it could be now time to see very crowded maps for players at all levels.