This has been my experience for season 1 so far from ranks 15-10 or thereabouts when I started keeping track.
Warlock has two very strong decks right now that appeal to a lot of players since you can either go aggro or control, and the aggro warlock is inexpensive to make so that helps its popularity I'm sure.
(I haven't really started the grind yet, I need more data)
- - - Updated - - -
I'm willing to bet its not as bad as you're making it out to be, although I don't doubt Warlock is the most popular class