No the point of the tier list is to help balance in the groups because when you have in a 5 people group a soulborn, a scout, a duskblade,a sorcerer and a cleric it will not so fun for the first (even if he optimize like the hell) the second will have his niche but the other will be better, the third maybe will do more damage than the other, while the first two will be the main people of the party.

One could easily play a tier 4 group. One figther, one scout, one shadowcaster and one incarnate, they would have their role (if they do a good teamwork especially for the incarnate) and it can work better for all the player (as a game ) where all of them are essential to the party while in the first the cleric and the sorcerer would have the upper hand in many situations