Classes Questions

Hi, I've been playing for a few weeks now and am hooked. I have a couple questions concerning classes..
1.) How well distributed are the player populations in each class? I recently picked up Nightfall and was interested in playing a Dervish... until I saw the first city literally flooded with them. I'm one of those guys who tends to avoid classes like that- is it really as bad as I think it is?
2.) In PvE, to what extent are certain professions shunned? I phrase the question that way as it's inevitable that the cookie-cutter builds will be most popular, while less-inoculated builds will raise doubt. While I'm carefully considering the synergy with the second profession for each class, I do want to experience all of the professions. I don't have two characters with the same primary or secondary.
3.) Not involved in classes, but what the hell: how do I make my characters walk, not run?

mesmers, ritualists, assassins, and paragons are really underrated classes mostly because people who haven't played them don't know what or how they work.

in general people hate paragons and rits r generaly not used and assasins r more of a pvp class but if u wanna get into a group easly monks warriors and eles get into them fast

To echo jhu's thoughts, Mesmers, Dervishes and Assassins are less popular in PvE, partially because it is hard to understand how they are helping the party unless you have played one.

The Dervish and Paragon were two new character classes introduced in nightfall, so don't worry about seeing lots of those two classes in the low level areas. As you gain in levels and start exploring other areas, you will see that they are less common.

I don't think there is an easy way to just walk. There are some skills that slow down your movement speed, which make you look like you are walking.