@Wolfie, where did that list come from? It's interesting.
@Vampire, if you're talking PVP only (since you said you want to avoid PVE) then I think it's difficult to figure out "top dog" since it changes pretty often as they put out balance patches. Initially Riftblades were the top dog, but now I'd say it's Pyros, but they are fiddling with Pyros in the patch next week. So I would say pick what appeals to you, really. The soul mechanism gives you lots of flexibility.
As for the list of least and most played classes, at least within each class, the Mage list makes sense - Necro and Elementalist both have pets and are therefore very popular for leveling. Chloro gives you heals, Warlock has the life tap for mana - all popular. Pyro and Stormcaller aren't as popular since they are both pretty mana intensive. Archon and Dom are not popular in leveling except as (typically) the 0-point souls. Archon, however, I've heard is very good to have in raids since the buffs/debuffs they provide are quite useful.
As for the Cleric list, I'm not shocked Justicar is most popular, as they have a ton of survivability, and the current "top dog" spec is often two of Justicar/Druid/Shaman. The healing souls are popular as second or third souls, with Warden being least popular due to them having mostly just heal over time spells, versus the Sentinel instant heal and the Purifier shield at minimal point investment. Cabalist as least popular doesn't surprise, as their spells are pretty mana intensive. Inquisitor being near the bottom is somewhat of a shock, as they are an awesome class, and Inquisitor/Justicar/x is a beastly leveling spell once you get some of the higher level Inquisitor abilities.
Warrior and Rogue lists I dunno about, though Beastmaster being popular for Warriors is no shock, and I'm not surprised Rangers and Bards are the most played. Rangers have the pet and Bards are pretty awesome.