Impossible. But hey, do a project, level all classes to 75, equip them with equal gear and post the results, i am interested in that too :3

The dps on dummies is almost useless imo, there are too many difference when you are dpsing on a real boss

This is the most accurate source for a dps rank: aionpveranks.com

You'll never have an exact ranking since classes have different advantages and disadvantages towards certain targets and the amount of targets - and people play classes too differently and have different computers, internet etc. The capability of classes is more or less known though due to making endless comparisons over the years.
The top classes dpswise have always been sorcerer and assassin, followed by classes such as spiritmaster, gladiator, cleric, gunner, bard, ranger, templar, chanter and last but not least aethertech. The mid-range classes aren't defined that clearly since they tend to switch positions, but one can easily state that sorc/sin are the strongest while aethertech is the weakest class currently in most situations regarding their dps. Some classes like templar or cleric for example profited a lot from their 180 CP skills introduced with the update while some classes maintained their position over the years (Sorc/Sin/gladiator for example) or even became weaker because they lost their advantages (aethertech => before stronger due to critspell when other classes still had to rely more on MBoost, nowadays with Knowledge as a stat this advantage is gone).

Some classes are depending on time a lot as well due to certain buffs - so whatever you compare, if it's different classes it'll never be that accurate though you get a lose ranking in the end.

Solo target DPS in general imo:
Sorc=Sin>Gladiator=SM>Cleric=Bard=Gunner>Ranger=Chanter=Templar>AT

That changes with type of instance, some classes like short fights more than others. Physical classes are heavily depending on chanter support and more expensive to gear pve-wise.
Other than that, aionpveranks gives a good idea what classes can do even though all Instances except Narakkalli and MoK seem pretty outdated with current gear progression.

AT is that bad nowadays? I remember in 4.* it was quite good DPS on single target bosses like the siege ones. No wonder nobody is playing AT these days.

AT was okay when it was the only magical class that could make effective use of critspell. Nowadays that advantage is gone thanks to knowledge stones.