The Barrows Brothers was one of the few runescape boss's I've ever done because they were solo boss
Not everyone likes groups for many good reasons such as other players being ******'s, and other players being even bigger ******'s when they kick you from the group as soon as you make ONE mistake runescape gold, like humans aren't supposed to make mistakes or something.
Basic economics. We do not want players being able to make money too easily. We also do not want high level gear to be too cheap, but not so rare that no one uses it.
As such, we have to strike a balance. If the armour has a fairly high drop rate, and we want it to be ~200m in value, we make the dropping monster require 5 people to kill. This way, only the very best (who can solo a 5 person monster), are getting a full 200m drop to themselves.
I think that it is 4 people period, no more, no less. They could make them soloable but extremely hard or team content, but if you bring more people it gets easier and easier to the point where farming is cheap and easy. I think that needing a team to get runescape 2007 gold high leveled gear is the only way they could do this.