#1: What would you think of a, say, Roman Catholic diocese, that took two years to release a few priests from their callings, and another 11 years to ex-communicate them, oh, let's say for "minor dabblings" in mass murder? Exhibit #1: Isaac Haight, the hate Mormon.
The church doesn't excommunicate someone for murder unless there is a confession or conviction in a court of law. It is not the job of the Church to dig into the lives of members and try to find some cause against them.
#2: You said it was the job of law enforcement officials, not the church, to find the perpetrators. Well, again, what if a local diocese knew that a local RC church included dozens of mass murderers? (You mean, no action, no investigation would even be launched? That would be the job of only "law enforcement officials"? And if that's the case, how is it that Haight & Lee got ex-communicated 13 years later--if the role of investigation belonged to law enforcement alone?)
#3: The fact that Governor Cumming (at the behest of U.S. President James Buchanan) declared amnesty for all hostile acts by any persons in the course of the Utah War hindered efforts to fully investigate and prosecute the crime. Many legal authorities considered MM covered by this amnesty.
Any real case of even suggested "amnesty" needs to have real people involved. You can't have phantom victims, and you can't have phantom combatants or perpetrators (combatants if a war covers them; perpetrators if not). The fact that we had mass Utah cover-up of the victims; and the fact that we had no combatants or perpetrators step forward to personally claim the umbrella of war, suggested a phantom apologetic on your part.
I think you're missing a major point. At the time of MMM and for quite a few years thereafter, there was just no distinction in UT between the Church and secular authorities. It was an outright theocracy, mitigated somewhat at times by the federal and military authorities. The same men held Church, militia and territorial offices simultaneously, as was the case with those who planned and perpetrated MMM.
If there was a conflict between Church and secular authorities, there is no question the Mormons would obey the Church.
You can’t just look at the date MMM happened. It took time for the facts to come out and there was a deep Us vs Them mindset that biased them against believing accusations. They also had good reasons to question if anyone arrested for it would get a fair trial.
You are ignoring the historical context and using hindsight to condemn them for not acting by some unspecified, arbitrary deadline, even though you don’t really know who knew what when, or even what specific charge it was they were ex’ed for.
Fault-finding is a lazy sport anyone can master. People who want to find fault can find it wherever they want to, even in the Savior. If the Church had acted quickly, you could just as easily be posting here today that by acting quickly the Church showed that it knew what happened very fast, so they must have been in on it, and they were trying to quickly toss those guys under the bus as part of the cover up.
Bottom line is the Church doesn’t toss members aside based on rumors, accusation, hearsay and alleged crimes. That means it can be a while before someone who should be ex’ed actually gets shown the door but it is better that than for a worthy member to get railroaded out undeservedly. We all will stand to be judged of God, and being a member there only means you should have known better.