The companions seem to actually serve a purpose. The fighters guild merely mercs for hire, with coin being the only common bond between its members.Even when not part of he companions it is great running into them every now and then. They have inadvertently helped me out of a few tricky situations in the past but from another point of view i do miss the guild quarters in every city approach. They all had unique quests and stories to follow. Also, the companions should have played a larger role in game. I have the feeling they would add legitimacy to anyones claim to the throne of Skyrim... given their origins.

Those who consider the fast advancing incongruent must have missed pretty much everything.
The Companions is not strictly hierarchical, there is Shield Brother/Sister, the Circle which is unofficial and Harbinger which is NOT a position of leadership .
The Harbinger is NOT the same position as Grand Master of the Fighters Guild.
Kodlak says that he is no ones Master and he is quite correct.
It is a much more informal title and position.

Have you read the old mans Journal?
Spoilers:
http://www.imperial-library.info/content/kodlaks-journal
Has it gone unnoticed that he was grooming you for the position as Harbinger?
Skyrim is more meritocratic, a remnant of ancient dragon values that the strongest rules.
Please, take some time to review your Dragonborns actions, successes and triumphs in the Companions and College of Winterhold.
Totally badass, no?

Rapid advancement is hardly unprecedented IRL.
The precedents are many, from Napoleon Bonaparte, Jean-Baptiste Bernadotte and quite a lot of my ancestors over the centuries.
Nothing succeeds like success, everybody loves a winner.

I did not like the companions at all. Maybe it was the fact that they weren't traditional werewolves, maybe it was the fact the quest line was so short, maybe I just like the fighter's guild more. Don't know, just didn't like them.