I'm probably in the Elo where I don't face stellar opponents but I actually do like to play Nasus a lot and always bot. I find that he can actually hold his own against almost anyone and in fact shove almost anyone under their turret.
By going R > E > W > Q, you can actually have exceptional harass and wave clearing ability and a maxed W is extremely good gank control (both in avoiding and assisting).
What I've found very effective is to basically handle bot for a while (if you're doing it right, they will change up bot about 2-3 times), that's when you switch up and go top. Wither is an amazing counter to anyone that relies on auto attacks (YMMV will vary but I find Jax isn't that hard to beat when his AS is slowed by Frozen Heart + Wither).