Talking from experience here, at 27-ish in the abyss, we ran into a full blue geared gladiator on our SM, this gladiator was killing mobs in mere seconds, no longer than 7 or 10 seconds. Our DoTs couldn't even take effect when we grouped for the elmos attacking us in the abyss. You can got aion online gold from the mods you killed.

when we got our templar to 31 and got her in full Daevanion and socketted full crit, our damage sky rocketted and mobs died before we lose 100 or 200, at the time, 5700+ HP.  We also parsed damage and DPS in groups and we always came top except for the occasional equally or better geared but higher level sin or ranger or AoEing equally geared gladiators in Aion.

Sorcs only started to do more damage as we neared 40 and told them to AOE and not CC. So a geared templar will level faster than a geared gladiator due to close damage but with much less downtime than a gladiator. Another fact is the endless groups you get in. Also tanks control the pace of the groups, if you learn to speed up your runs expect FAST leveling(aion powerleveling) only limited by your group's mana and total DPS.

Just remember the solo experience is on an very good geared templar as we are very gear dependant. We scale very good with gear so we found out we do better than equally geared classes. In PvP, we really feel bad for gladiators as they only start to bloom at 50, but even then they have trouble against certain classes. We hope the next patch fixes that for them.