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
Spectre's and Reapers do a lot more single target damage than people give them credit for.
Most of the time they don't is because they are too busy holding agro and don't take advantage of the 25% back-damage that the other players are doing on single-target boss/mini bosses at raids.
The fact you don't rate them that highly as well, shows you also don't know much about the full mechanics of end-game, either.