3 of those 4 you mentioned are extremely toxic. Rattlers may not be like Elapids but there are PLENTY of Pit vipers and True vipers out there that will kill you in a heartbeat. I had a few close calls with Rattlers, some wild, one was my own pet lol. I think the Mojave and Northern Pacific Rattlers have the worst bite in American viperidae, but I'm pretty sure atrox, ruber and helleri are right behind them.....I did learn early-on that horridus and adamanteus were very high as well......the Diamondbacks are double-dangerous due to their highly potent hemotoxin............I'm in Cali. We have a huge variety of rattlers over here but what I encounter most are southern pacifics but I've also messed with western diamondbacks, red Diamondbacks and sidewinders
.....but also because they have MASSIVE venom glands and are not afraid to deliver a lethal dose. Careful with that one lol When it comes to striking, Rattlers are certainly as fast maybe faster than Elapidae, they just have different locomotion so they can't SET-UP a kill strike nearly as fast because of the way they move and reposition their bodies.
Mambas?? I'm not that good yet, My Friend. One day.