Barquiel wrote...
The Yahg was neither competent nor trustworthy. He was just greedy, that's all. The Yahg knew that the reapers are coming. He knew that the collectors are protheans...and he still made a deal with them (because the payment was good). Liara barely had about 6 months of being the Shadow Broker before Cerberus attacked her, presumably even less than that considering it happened before the Reaper attack on Earth. Meanwhile the Yahg had decades of experience in the business before Liara killed him. What makes you think he would have come to the idea for the keys in the next 6 months? Liara is going to Thessia to ask her mentor because the Yahg had nothing, just a vague idea.
You're begging the question here. You're arguing that the fact that because the Yahg broker didn't find the information in the prior decades as Broker, he was incapable of finding the information. This is a combination of chronological snobbery and the Historian's fallacy.
To clarify as an example, say you have an archaeologist who's been working for years around the world trying to learn about a civilization and their lost treasure. He hears from second hand sources about the existence of a cache of gold somewhere in the world. Before he can find it, he's killed by another archaeologist. He leaves behind only his notes as to the possibility of the existence of such treasure. The other archaeologist goes on to study more sources and gather more information based on this specific treasure. Eventually, he finds it.
Does this mean the first archaeologist was incompetent? No.
He was completely competent. In fact, look at his track record. He's very well known, and very well regarded throughout the galaxy for his skills and ability with information. He was greedy, and justifiably so. He was out to survive the coming holocaust. I'm not saying he wasn't misguided in how he chose to perform his plans (by making deals with the Collectors), but he was doing what I'd do in trying to survive. Where would Liara be if she hadn't become Broker? She learned about the existence of such rumors about the Prothean weapon from the Brokers files. Just because he didn't have anything concrete at the point where Liara had nothing at all. Look at my example. As for trustworthiness, I'd say that he knows he can't bargain with the Reapers. I'm sure he knows they're coming. He may not be trustworthy by nature, but he knows what will happen if he isn't trustworthy. So I'm more than certain that he'd devote himself to helping fight the Reapers in any manner he could.