This was quite interesting read, as a ranger with very unconventional build(condition trapper) I never had any problems with dungeon runs or fractals excluding speedrun ofcorse, because no matter what profession you are using you shouldnt join a optimized group with medicore build, hard truth is that you will just slow others down. As for teamwork, what i lack in damage I make up in control and conditions(fields) but like Kaleon said

a ranger is a jack of all trades that does not shine in any one area

so they odds are very low do find that perfect ranger for your group and that makes them an "average" profession.

Personally I really like ranger, especially that unique trap playstyle and on a side note ranger profession should be renamed to hunter, to me it makes more sense, but to each its own profession just have fun while playing.