Uh, there is a difference between seeing an event differently than others and not seeing an event and claiming you did. One is illegal the other is not (unless you can prove the witness was lying). Not a single witness was both consistent and whose testimony matched exactly with another's eye witness account. Some witnesses were consistent but their testimony wasn't corroborated by another witness or physical evidence and some witnesses did have a matching story of another witness but their testimony wasn't consistent (ie they told the police something different than what they told the jury).
None of that matters as the job of the prosecutor in an indictment is to show there is evidence a crime was committed, not to prove his case before a grand jury, that's what a trial is for.
Had this been a normal indiectment, one the average citizen would face, the prosecutor would have presented evidence to make his case. So they wouldn't have had known false testimony, they wouldn't have had the accused testify, and they wouldn't have questioned witnesses that would have given testimony that would hurt their case.
It's why indictments return a true bill 99+% of the time and it's why there is a saying that a prosecutor could indict a ham sandwich, because the prosecutor controls the whole process. It's also why indictments don't carry any weight as to the guilt of the accused. Honestly it's a pretty pointless process that has been perverted.
I guess you didn't bother to read the article, so I shall quote the relevant parts for you:
One woman, who said she was smoking a cigarette with a friend nearby, claimed she saw a second police officer in the passenger seat of Wilson's vehicle. When quizzed by a prosecutor, she elaborated: The officer was white, "middle age or young" and in uniform. She said she was positive there was a second officer even though there was not.
Here's one witness that I referenced above, she claims to have seen another officer in the car, but there was not. Are you saying she's able to see people who aren't there or is the more likely answer that she was making it up? Next witness.
Another witness had told the FBI that Wilson shot Brown in the back and then "stood over him and finished him off." But in his grand jury testimony, this witness acknowledged that he had not seen that part of the shooting, and that what he told the FBI was "based on me being where I'm from, and that can be the only assumption that I have."
The witness, who lives in the predominantly black neighborhood where Brown was killed, also acknowledged that he changed his story to fit details of the autopsy that he had learned about on TV.
"So it was after you learned that the things you said you saw couldn't have happened that way, then you changed your story about what you seen?" a prosecutor asserted.
"Yeah, to coincide with what really happened," the witness replied.
Here we have a witness telling police a blatant lie as the witness did not see what transpired. Lying to the police during an active investigation is indeed a crime even when the truth of the testimony is revealed during a GJ hearing. Next witness.
Another man, describing himself as a friend of Brown's, told a federal investigator that he heard the first gunshot, looked out his window and saw an officer with a gun drawn and Brown "on his knees with his hands in the air." He added: "I seen him shoot him in the head."
But when later pressed by the investigator, the friend said he had not seen the actual shooting because he was walking down the stairs at the time and instead had heard details from someone in the apartment complex.
"What you are saying you saw isn't forensically possible based on the evidence," the investigator told the friend.
Shortly after that, the friend asked if he could leave.
"I ain't feeling comfortable," he said.
Here a witness testified at the GJ hearing to something that he or she admittedly, when pressed, didn't see. I'm not sure how you would like differentiate this testimony from witness 40. Witness 40 is quite literally the flip side of these three other witnesses. All of these witnesses had an agenda and testified or provided statements in support of that agenda. Then when pressed during the GJ hearing, had to recant by stating that they did not actually witness the events that they testified or provided statements for.
Regarding the second half of your argument, it's already been discussed ad nauseum in the main thread in which you participated in, that had this been a normal case, it would not have even gone to a GJ hearing. The physical evidence in this case align heavily in favor of Wilson's testimony. I know you will retort that the prosecutor should have had the courage to not bring the case to a GJ hearing at all than instead of hiding behind the GJ, but as it's been explained, the way the GJ was used is only rare but not unprecedented and is typically used when it's a high profile case.
To address your last point, I entirely agree that prosecutorial discretion has been heavily perverted, but the solution is not to make it so that GJ hearings wrongfully indict more white people and police, but to make all GJ hearings more akin to the Wilson GJ proceeding whereby the GJ has the opportunity to see all the evidence and testimony. Here's an Op Ed addressing this viewpoint:
http://www.washingtonpost.com/news/volokh-conspiracy/wp/2014/12/06/harvey-silverglate-on-fergusons-unexpected-lessons/