There are some older ship class guides out there, but the game has changed a lot since then. Also, I'm not sure that mass is the best basis for classifying warships, since mass is no indicator of function or relative ability. Function (i.e. drone carrier) could be a means to determine relative class, but classing by function gives no indication of firepower or shield capacity (a fighter can be 50 mass or 50K mass, serve a similar role in battle, and have an impact upon battles that is worlds...
Classing Ships for Fleets
Classing Ships for Fleets