I understand how you feel, I thought the Thieves thrust you into a position of power to soon at first as well. Then I did a single quest, and some radiant quests, then another quest, and more radiant quests, then it made more sense, if you take time and do the guild "side quests" it makes more sense IMO.
Now, the problem with this it the Companions don't let you do this, you do one side quest then you seem to be forced to do another "main" quest, Ill have to test it but so far thats what is seems like.
Yay, another rant. Let's have more of these.
Dude, I think you need to take a break from these forums, you are not being helpful or constructive in the least.