The 2 set swapping is effective at keeping you thinking about building your own sort of archetype.
I find it much more flexible than GW2 in terms of the choices because of the very strong effects that weapon choice actually has on your character. Weapon choice focus can drive party-role more significantly than class choice - which is different than GW2 and many other MMOs.
I've definitely worked with both DK & NB tanks who had similar weapon choices and were both quite effective at their roles.
Now, for someone like a sorcerer, it ends up driving your role between Heal & DPS since it's quite common for a Sorc to pick a restoration staff as a second wpn type. Plus, they can switch out to their DPS set during combat if the health levels are nice. Very appealing to the normal sorc situation where they can't get a party because they are solely DPS. ;)