A 5 Scourge party has limited mobility, limited access to boons and even less ability to share them, vulnerability to CC, limited ability to engage beyond 900 range and none past 1200, and no active damage mitigation other than barrier. They also rely heavily on the generation of Life Force to be effective. In other words, all the classic weaknesses of Necro but without Life Shroud. I fully believe that Scourge can do too much with too few skills, but you're focusing on what they're good at and overlooking what they're not good at. Like you said, they do have counters and part of the solution to the Scourge problem is the use of those counters. My concern is that Anet announced Scourge nerfs and some people seem to have taken that as a cue to continue blobbing into the Shades because the balance patch will make that viable.