If the Asari told Shepard and friends sooner the temple could have been made more secure or Vendetta could have been moved to a safer location, like how Kai Leng moved him to Cerberus HQ. Upon discovery of the Crucible requirement, Vendetta could have been moved to the still under construction Crucible to smooth things out or hacked like what Cerberus did.
At the end of the day the Asari government: 1) broke the Council law they themselves added, 2) because of this steps that could have been taken to secure Vendetta were never implemented. What make's this all frustrating is that it is heavily implied the Asari did this for purely political reasons when all the races are facing complete extinction. Sure maybe the Councilor is unaware of the beacon (although I have trouble believing that), but that does not excuse the Matriarchs or whomever was in charge of all this secrecy. What makes it worse is that Shepard is railroaded into being sad for the Asari when he had the option to be callous towards the other extinct or dwindling races he was involved with.
I'm a big fan of sentient, blue skinned, bipedals in the Mass Effect universe; but the Asari government is responsible for the crime of standing idle and letting politics dominate their course of action in ME3. It's frustrating that the Matriarchs are some how immune to Shepard calling them out on their crap like he can with every other dumb, self serving politician in this game; instead the only option we have is to feel varying degrees of deep sadness for them.
The Asari had Asari Commandos guarding the temple. Do you know about Asari Commandos? 5 of them killed 100 Bloodpack mercs on a slave raid until they were relieved. That was the Serrice Guard. The Turians say that "Asari Commandos are the finest warriors in the galaxy. Fortunately there aren't too many of them." How could the temple have been made more secure than it was being guarded by Asari Commandos?
It wouldn't have mattered. You're not getting it. What ever was there was taken out by plot. Kai Lame cloaked, got inside, and killed the scientists and waited for Shepard.
How did Cerberus find out about the temple? Was it because Bioware was too lazy to have Councilor Tevos or Irissa take a walk with Shepard somewhere other than the obviously bugged Udina's office? Again failure by reason of plot.
Trust me, if the temple had been revealed earlier, Cerberus would have been there, or something else would have gone wrong at the critical moment. There would have been a Cerberus mole on the Crucible project among those scientists you rescued with Jacob who would have tipped off TIM that a Prothean Beacon was moved to a secure site nearby. TIM would have found out.