In my opinion for Raids and boss/single-target dungeons:
A: Spectre, Templar
B: WL, SS, HK (sometimes need but never a shortage)
C: Reaper, Wiz, Knight
D: Ranger, guardian
Basically since there's no content strong or diverse enough to need a dedicated tank or ranged dps, gladiator is king since they do substantially more dps than other classes. Gamigo refuses to or is not competent enough to make balance changes to resolve this.
For pvp I think it's much more balanced with all classes being relatively viable and good in different circumstances