While I can see how it seems very unfair at first. It's really not.
Drawing cards for Runners are worth less clicks than credits are for Corps. Therefore the 4 credit cost to activate Snare is actually quite reasonable. Add to that that you want to run 3 of it to decrease the randomness of it. That's 6 influence outside of Jinteki. And just like every other Jinteki trap they are best outside of Jinteki. That doesn't prevent most of the Jinteki decks from playing 3 Snares, though. But against Jinteki you're prepared.
While accessing a snare from the top of the R&D seems like random luck, you'll have to take into consideration how high the chance of hitting stuff you want/don't want. Assume your oponent has 3 Snares. He also has 3 Nisei MK II, 3 Private Security Force and 3 Priority Requisition (with Core only). So out of 12 worthwile cards 3 are Snares. While it's higher chance to hit an Agenda, it's not that low chance to hit a Snare. Assuming you hit something worthwile, which is not true in many cases. Which is why R&D runs are mostly good for knowing which cards the Corp will throw at you.
Also, if you play a couple of games against Criminals, you'll notice how good the fact that Snare exists is. They can be aggressive, but the mere possibility of you running Snares will hold them back a little. It's one of those cards that are needed to make sure the first two turns aren't, Run, Run, Run, Run.
Speaking of Criminals, they are the main reason why I don't think Replicating Perfection is that good. Between Desperado and the often splashed Data Suckers, they just make a run on the cheapest central and get good benefit from it. ICEing Archives is good and all, but unless it's an ICE that hurts you, you'll be fine. Any ICE that "just" end the run is basically only a click extra to run a remote server. And protecting three centrals is MUCH harder than protecting two (which is the usual way to do it). It's the reason why Sneakdoor Beta is such a good card.
I don't want to sound judgemental here, but the best way to keep the Corp player in check is to run a lot. Make him rez ICE that's how you keep their economy down. By being aggressive you'l limit their plays. That's the strength of the runner. If you let them bank 10+ credits you'll be sitting there guessing what ICE they have and how many Agendas they can score off their SanSan that they haven't even rezzed. If you do that you'll see that it's not uncommon for the Corp to sit on less than 4 credits when you access cards. And then you really benefit from hitting that Snare.