As part of the 'Flameseeker Chronicles' series, Rubi Bayer of Massively had an interview with John Stumme (Guild Wars 1 Live Team Lead) and Eric Flannum (Guild Wars 2 Lead Designer):

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Massively: Moving on to Guild Wars 2: What sort of factors were taken into consideration as you began planning both the PvP and PvE sides of the game?

Eric Flannum: We treat both the PvE and PvP aspects of the game as being equally important. When we first sat down to plan the game, we knew that we wanted robust PvP and PvE, and we also wanted to introduce a third type of content that spanned the two with what would eventually become WvW. It's very important to know and recognize how all of your systems will interact with and affect each other.

For example, one of the first major decisions was eliminating the concept of dedicated PvP characters from the game, deciding instead on a system where you took the same character into each of the different game types (PvP,PvE,WvW) and your character changed to suit the game type as they needed to. So in PvP all characters can be set to the same power level and have access to the set of skills we designate for PvP while still being the same character you play in PvE.

We felt like this helped tie the different parts of the game together and place an importance on the player's identity as a specific character, which is of course an important aspect of all RPGs. This decision has had a profound effect on Guild Wars 2, and it's a decision that we could only have made by knowing that we value PvE, PvP, and WvW equally right from the start of development.
Check out the full interview here