As to the idea that archetypes can solo, albeit slowly, is it really enough just to make them more desireable in groups? Do you realize just how much more slowly they DO level?
At L30 I calculated that at my current rate of killing even con minions on my empathy defender, it would take me 200 hours of solo play to finish up the level I was over halfway through. I then walked around a blind corner into a boss, died, and got far more debt than xp I had earned in the last two hours of xping. At that point I realized it was pointless to play the character anymore, and started up a blaster.
Excelling in a group, as your strength, is fine. It sucks, though, when your two best powers aren't self-castable, and soloing just isn't an option anymore. Like it or not, you just will never ALWAYS be able to have a group. It doesn't feel very heroic, that's for sure.