Some thoughts:
Warhammer Online DOES suffer from underpopulation as a result of a bad director. The head of the company - Mark Jacobs - was incompetent at getting things done and mostly did what HE wanted and not what the fans wanted. As such, there was junkyards of new content which nobody really wanted and "blanket nerfs" - that is, the nerfing of a whole entire archetype or so because of one class. In a few months the population dropped from 750,000 to around 300,000, where it is now more or less stabilized. Mark Jacobs was fired, and - thankfully - the updates now seem to be much better. However the damage is done; many fans on the forums seem to be disgruntled by the months of inaction by Mythic (the maker of WAR) and aren't too pleased.
As thatguyyaknow said, the lack of population isn't a problem if you choose a server like Iron Rock, Gorfang, or Volkmar. (However, if you want to create a Destruction character do not choose Dark Crag, which is going through major population imbalances skewed to the side of Order.)
And about the White Lion (for the uninitiated, the High Elf Melee DPS) armor fiasco: they were the last class to be implemented into the game and thus suffered from a lack of polish for the longest time. They still look pretty bad throughout all levels, but Mythic is currently going through a project to redesign all the armor sets in the game. I can only assume that they will be improving White Lion armor and giving them the kilts they had in WHFB and not the dresses they have now.
White Lions are actually an amazingly strong class right now because of a bug that allows one of their "procs" (essentially, their reactionary abilities that hit the opponent under special circumstances) to critically hit. This led to much complaining on Destruction's side, to which the design team said that if they nerfed it they'd gut the whole class.
However, they have more or less fixed pet AI with a small bandage, which makes pets "stick" to the target after they've gotten to them. Unfortunately, this makes them immune to "detaunts," snares, and roots (which only exacerbates the proc bug). Keep this in mind if you want to play a White Lion (which has a lion as a pet - another small break from lore) or a Goblin Squig Herder (the Greenskin Ranged DPS).
To add another class to the "Do not play" list: Witch Elf. They're not too great right now and while they're not the worst they won't be getting buffs anytime soon like the Marauder or Magus.