Is it better to let the council die or save them in ME1?

What motivation do the Asari actually have to tell Shepard about their Prothean Beacon in ME1?  The plans for the Crucible haven't been found yet so there is nothing to suggest that sharing their beacon with the humans would solve anything... particularly if the Asari haven't actually figured out how to activate it yet.  In ME1, Shepard is looking for the Conduit, but should, by your own assertion, have figured everything out on his own after obtaining the cipher from Shiala (and conversely not been able to figure out the Asari beacon before receiving the cipher from Shiala.  It's clear that Shiala was unlikely to even know anything about the Asari beacon since it was highly classified and, as she said herself, there was nothing special about her."

It's unlikely that Bioware would have written the story in such a way that those many lives would have been saved.  They would have merely come up with a different mechanism to ensure that Shepard's access of the Asari beacon made no tangible difference.

So, do you agree then that, as the game is written, the Asari might have some motivation for being suspicious of Shepard and Anderson and have a reason for keeping the Thessia beacon secret at least through the entirety of ME1:  If the beacon might contain blueprints for weapons of mass destruction and "Saren took" them (as Anderson believes), then a possible motivation for Shepard wanting to go after Saren could actually be just to get those blueprints back for humanity and the Reapers just being a convenient excuse rather than a serious threat to all life in the galaxy.  The multi-species council may not even be around at all throughout ME2 so it's hard to suggest that the Asari councillor should have fessed up about the Asari beacon then.  That leaves only ME3... when there is still no indication that any of the beacons contain any helpful information about the Catalyst... since none of them accessed by Shepard throughout ME1 or ME2 contained anything more than the generic message that was transmitted (albeit damaged) in the first one and potentially no way for the Asari to be sure their beacon would convey anything different (particularly since vigil, at the end of ME1, basically tells us that the same message was sent out across the entire beacon network).

The plans for the device, however, were not found in a beacon; but rather in archives.  As I said, throughout ME2 Shepard encounters some beacons... all of which only contain the same information as the first one.  Why would anyone have cause to believe the Asari beacon would contain the answer to the Catalyst rather than simply assume that it would most likely be like all the others?

IMO, it's a "miracle" desperation caused her to take a long shot and send Shepard to Thessia "just in case."  I also don't think it's a coincidence that she chooses to wait until Udina is out of the picture (due to suspicions as I mentioned previously).  I'd be more inclined to write the game to head back to Mars to scour those archives even deeper to see if the missing piece to the blueprint could be found where the blueprint itself was found or to draw in a mission involving the Citadel Archives (instead of just chasing Shepard's clone through the building).