I think that is a good way to figure out what a person wants to play, but I'll have to refute that it isn't the "best" way. Subjectively, you may value it more than doing PvE to figure out your class because you devalue the spoiling of content and because it is faster to do sPvP than PvE, but each person has their own way of figuring out their own soul in a game.
To each their own. I would never do PvP to try and figure out which character I wanted to play for a game before I would do the progressional story building and valuation via doing PvE. In PvE, some people love the whole progressional style of play that it allows and feel that it makes a stronger connection with their character. It's all about the subjective appeal to what a person wants.
Each way has its benefits. Along with those benefits, each way carries flaws. It is all about the appeal of the person that matters. <3
Bona Dea Ubume