First to say that a scrapper is in a "riskier" position than a blaster and therefore his damage cap should be higher is foolishnes.
A scrapper or a tanker with their armors, defenses, cloak of fears, draining life toggles, point blank area effects (such as fire tanks) can take more dmg to themselves than a blaster can. So what the ranged attacks of a mob do less dmg than the melee attacks... when a blaster is hit by a crey power tank, they go down no questions asked.. wheather by melee or by grenade. A scrapper or tanker gets hit by this and they shrug it off.. especially after 30th level.
You say the base line is 3 white mobs. I have yet to see a blaster at 30+ take 3 white mobs and not be wondering if they are going to fall and get debt (hence the nickname debt magnets). I have, however, seen Tankers take on slews of mobs without getting much more than a splinter in their pinky. Case in point.. traveling through Perez one day, searching for badges with my defender alt, there i see a fire tanker running from 50 (no exxageration) hellions. I target him thinking he may need a heal.. but his health is full. He runs them into a corner and soon enough all 50 are dead. I kept my target on him and his health never dropped below 3/4s. Show me any archtype, besides an illusion controller at 32+ level that can do that. Is that what you call a base line?
Lets also look at the slider. Blasters for the most part have to keep their slider at soft shelled taco.. Tankers and scrappers however, keep theirs at Titanium gonna take on Galactus and the gods of Mount Olympus.
Blasters have become the red headed step child of the CoH game. Even the ancillary power pools of blasters, with few exceptions, are no more than secondaries from the blaster sets. I am a fire/ energy blaster my ancillary is fire mastery and my power slots for those i would have gotten at a lower level if i were a fire/fire blaster. Granted there are exceptions like the force fields. But at 41st level to have a force field single slotted does very little against a 41st level mob. You would never see a force field defender walking around at 41st level with it single slotted because at that point it would be useless to him.
You also say that Scrappers are involved in melee.. and this is true... until the ancillary slot where they gain a ranged attack. So at 41+ the scrapper and the tanker gain a ranged attack, more hit points than any other archtype, do more dmg thn any archtype, take more dmg than any archtype. Its no wonder that 50th level tanks are the primary source of quick powerleveling.
But scrappers and tankers are not the only ones with a definite unbalance to blasters. Take a look at defenders. My 35th level storm defender with electric as secondary took out a 50th level blaster in the arena.. why? Because my secondary blasts do almost as good dmg as the blasters (they are after all blaster primaries) and my defenses are much greater. My defender solos better than my 50th level fire blaster any day of the week. At 35th level he is taking on 4 or 5 red cons to him without really blinking an eye. Most of the time he is letting voltaic sentinal, tornado, and lightning storm do most of his work while tesla caging any that those dont take care of.
This brings me to controllers. You claimed earlier that controllers do little dmg in comparison to the other archtypes. This holds true up until about 32nd level. Once a controller gains his or her pets, they become unstoppable. Now i heard the arguements that this is to compensate for the controller not being able to solo at the lower levels. Blasters are debt magnets because they can not solo at any level beyond 15th.. unless they are real smart and real lucky. Controllers can solo at all levels. Let me give an example. Grav controllers are the best soloers in the game at lower levels. They can hold opponants while dmging them and thier holds are the best in the game, lasting almost an entire fight. Mind controllers have no problem soloing since psychic attacks are seldom resisted and have little defense against them. Illusion controllers are the same way... blind/spectral wounds. My 9th level Illusion controller did on average more dmg to a mob than a 9th level blaster did because spectral wounds is hardly resisted. Once the controller gains pets, all bets are off.
Illusion controller pets are either invulnerable or have such massive attacks the controller needs do little but heal them. A 38th level illusion controller can be a 10 man group all unto himself. Phantasm/Phantom army. One is indestructable with taunt abilities the other is a blaster who can summon more of his kind. Fire controller can summon up to 4 imps making them a 5 man team unto themselves.
So my question is thus... if tanks, scrappers, controllers, and defenders can do more, take more, and defend against more, than a blaster can... where is the role of the blaster.
I have seen 46th level controllers, tanks, scrappers, and defenders, take on entire groups of mobs and walk away as if nothing happened... i have seen each of these archtypes set their mission sliders to the highest point available and not blink an eye. I have seen blasters fall to mobs 3 levels lower than them in single combat because a blaster has not the dmg accuracy or defenses to do much against the onslaught. You will be hard pressed to find a blaster that does not have a hard time after 30th level doing anything on their own.
As a side note... if scrappers and melee types place themselves in riskier positions because of being in close.. why is the blaster the first to fall in most group settings... I can answer that as well. because their attacks draw lots and lots of aggro... And that, is where the real risk lay.