Another thing to remember about signets is that they create a lot of broken starts with 0-1 cmc artifacts (all the major moxes, sol ring, mana crypt). The old mana crypt->Signet->signet opener is pretty much unbeatable.
That said, I think it's important to be careful with taking that to extremes because when you have a lot of turn 1 ramp, CMC 3 ramp's value actually goes up in some ways, *especially* if that ramp is mana dorks.
Overloading on 2 CMC ramp is a good way to either flood or stall on mana if your deck isn't built right around those effects--meaning for example that signets are pretty great if you are pretty sure to gas up on 4 mana (since signets are the most consistent at bridging from 2-4). But they're a lot worse if you depend on hitting your first 4 land drops and going to 5 mana to hit your refueling spells (e.g.
Mind's Eye).
Reason being that hitting 4 lands out of 10 cards is not actually all that likely when you have 35-38 lands in the deck -- <60%), and if you need to get to 5 mana you're counting on that. So you need to be playing cheaper draw spells, or have some other way to gas up <5 mana if you want to be consistent at getting there.
For me there is no typical deck - every deck wants its own ramp profile. I've played many decks with no 2 cmc ramp at all, just 1 and 3. And one of my current decks has only 4 total ramp spells (sol ring, sapphire medallion, fellwar stone and dimir signet).
It's important to think about what you want to cast when and then build to facilitate that. If I'm playing a control deck in green I'll play the ramp that generates card advantage over almost anything else (
Cultivate et al, because they function as a 3 CMC draw 2 which is borderline playable in those decks on its own without the ramp).
In mana dork and extra land drop decks I almost always end up with huge bubbles at 1 and 3 from a ramp perspective (because burgeoning, exploration, sakura-tribe scout, azusa, swordtooth and cultivate make that pretty natural).
Zacama
