When dealing with normal trainers you'll probably outspeed more things than you'd expect, but a lot of things will still be faster than you. As for frailty, it is indeed pretty bad. It's generally 3-4hko'd by even weaker pokemon, and come late/endgame most good STAB moves 2hko you (hell, Iris's Hydreigon nearly OHKOd me with its neutral Dragon Pulse). Seviper also has a hard time OHKOing stuff back, since Poison Jab hits hardly anything super effective and it only has 80 BP, and its most of Seviper's coverage moves come very late. Even during normal trainer battles, it wasn't uncommon to be forced to switch out versus trainers I didn't even have a type disadvantage against, and rarely did I finish battles with even half my health remaining.