Hearts feel too grindy, and sadly they are a part of exploration feat in every area 'cept for cities.
Jumping puzzles are fun but they are few.
To level up you have to do hearts and events. These are too grindy to some people's tastes, including mine.
Especially considering that it is "end game", since you can "level up" beyond level 80 to gain trait points, afaik.
P.S. crafting is a quintessence of grind in almost any MMO (SWTOR is an exception), in GW2 it is particularly grindy due to the low amount of resources gained while casually playing.