If I recall correctly, in most/all of these cases, Shepard doesn't actually know about those missions in advance. The Rachni mission (for example) doesn't trigger unless you intentionally enter the system/cluster where they're located.
The Geth missions are pretty uncommon, relative to the number of exploration-based missions, but you're right they do count as investigation options. But again as above, many of the quests don't trigger unless we're intentionally looking for them. Even in the context of lead-hunting, it would be pretty insane for Shepard to be doing a system by system search for Saren, when he does have demonstrative leads available, like Noveria/Feros/Therum.
Thin leads. Two rumors of geth activity, and the estranged daughter of one of Saren's flunkies who may not actually know anything (and as it turns out, doesn't)
Do we really not know that time is of the essence in this instance? Let's put aside the Race against Time label (admittedly that would be a meta-game appeal). We know that Saren is after either human extinction/galactic annihilation and we're forced to accept these threats as legitimate. And keep in mind, there is no indicator that any/all of Saren's plans have to be committed in the heart of Council space (Eden Prime, Noveria etc are outside jurisdiction as I recall) or that he would even care about sending the consequences of sending his forces into certain regions of Council space (Feros is one example I believe). We could also reference the evil-genius nature of the Saren/Benezia recordings, that Benezia herself has Asari commandos at her disposal as a Matriarch, and that Anderson tells us about most of these leads at the same time indicating they're occurring concurrently. Whichever way we slice it, we're far behind, not ahead. Mass Effect is a race against time by virtue of the fact that we know Saren has a horrendous plan he is attempting to put into action, without adequate knowledge of the means.
Those factors aside, that still wouldn't be a plausible defense in any instance where investigation is warranted. "We don't know anything" isn't a counter-point, when your primary/overall goal is itself information-retrieval/discovery/galactic extinction prevention, which only gets increasingly more difficult the longer you delay. Investigations don't speed up/get easier as time wears on and in ME's case, we're forced to accept the Reaper annihilation/Saren threat as being extremely dangerous for us.
It's a bit like the detective films where they say "we expect the killer to strike again". You may not have an in-detail sketch of the murderer's exact plans, but he's always going to know his own intentions/plans better than you do, increasing the urgency of finding him. Random exploration into the traverse is not the way to do it.I indicated this above, but that actually indicates the other massive problem: many of the side-quests themselves hidden until you're in the system. That's not really lead-hunting, that's doing a planet by planet sweep.
Well, you will notice I didn't mention side quest structure as one of the things MEA could learn from ME!... 
But in the end, I believe the intention was that Shepard, out in the Traverse, would at times handle other problems the Normandy encountered and was in a position to help out with. Or wasn't, if your Shepard didn't want to
Retour en haut
. Seriously, the FOX News thing happened and we've passed that now Bio. 
