I have to agree, for the most part. However, Heimskr's uncontested preaching right in a main thoroughfare of Whiterun is a strong suggestion that the Thalmor have limited capacity in the city. Balgruuf is a Talos worshipper himself, and reluctant to choose a side in the war until it shows up on his doorstep.
I forget who, but someone earlier claims that Saadia's body ends up in the Hall of the Dead if you side with Kematu. I've never seen this happen. I was under the impression that Saadia is disabled by the quest, much like using a console command to disable someone or something.
If someone wanted Saadia dead, why wouldn't they just perform the Black Sacrament? Some people around here seem to believe the Thalmor are responsible for the random encounter DB assassins after the player, and if they're willing to go through a bunch of 'inferior' race Sithis worshipers, why wouldn't they have Saadia taken out that way?
Alik'r Redguards. Might have a better idea on where she is. The thing everyone is glossing over is that the Thalmor and Alik'r have no real knowledge on where she is. The Alik'r are sent to find her and have to use the Dragonborn to do it.
Also with the Dark Brotherhood (correct me if I'm wrong) but aren't all the targets you hunt down in known places.
You have to do some hunting to find the Gourmet.
Edit: Ning is having serious issues with comments! The rest of that statement just got completely cut off! =_= Anyway, I think the locations of all the other marks are known. Except for, you know, that pesky player character (until you join them and they decide keeping you as an assassin is better than fulfilling a contract to kill you).
Whatever the truth may be in this quest, I don't think it can be found with either Saadia or Kematu. As you said, Saadia's version doesn't ring true, but if a person is to be judged by the company they keep then I wasn't impressed by Kematu's choice of "friends" (the ones I had to kill to get to him) either. I ignore this quest now because neither resolution feels right to me.