I'm going to second Rumble.
I actually just played against Rumble in lane phase 1v1 on top and Rumble is good because he has a form of ranged(that will also slow you since you need to be near his minions to Q). His Burn will pressure either you or your minions and he has a shield.
His ranged E or something, whatever it is, can get from 1 bush to the other just fyi, gave up a kill because I didn't know that :-(

Just to troll, Lee Sin or Karma.

Lee Sin: You slow me? I slow you. You try to Siphon a minion? I jump to it, shield it, and beat your face in. And I just shoot sound at you every other second.

Karma: Slowing lasers! Shield bombs! Healing waves! Especially the shield bombs. Nasus will never Siphon a minion again.

I've only laned against Garen about 5 times but I've come out on top every time (yes it is entirely possible that I've been lucky enough to only get matched against **** Garen players). You can't kill him since he can cleanse Wither but there is nothing he can do to stop you from farming as long as you don't try to run from judgement.

If you are somehow losing it might be because you are using dodge yellows or something.
I find they are getting hit very hard by the power creep. Before there weren't a lot of champs that had physical damage skills, dodge was fine cuz the physical damage you take was mostly from auto-attacks. Now there are a lot of champs with physical damage skills and flat armor yellows are much better.

tristana
massive range, healing debuff, slow, scape and ult to keep him away

I've laned mid successfully against both Ashe and Cait (separate games) as Tryndamere. I have a feeling that shouldn't happen, but it's as you say: if the skill level is low enough, anything goes.

lol

The fact that you answered your own question amazes me...
I Love playing AP carry Soraka... Its not expected...
Lvl 1 Starter AP runes ectra + Ignite bonus = 47ap.
47ap + Starcall = 100 damage lvl 1 starcall.
2nd ability get silence
3rd starcall
your now starcalling 150ish damage a starcall... your Silencing for 100 damamge...
and Nasus never gets close enough to hit you...
If i'm not playing aganst 2 heavy ranged dps i can normally push 1 or 2 people out of lane with soraka... or even get kills bottom with just another support like Taric or tank like Malph...

Anything that counters melee farmers counters nasus. Teemo is probably the best counter, but there is swain, zilean, brand, anything you can think of that has a good range and a cc/speed buff so you don't get raped when he slows you.

Ranged harass comes to mind. An AP Teemo is possibly the most annoying enemy I could face at top.

Gragas does pretty well against Nasus. When that barrel rolls into the minion pile, the natural, and smart, reaction is to get the hell out of the way. So you're not getting last hits with Q, cause you can't stand in among the minions without getting blown up. You can't Wither Gragas because Body Slam is like a low cooldown Flash, so a slow doesn't do much, and laying Nasus' little circle AoE is hard because Barrel Roll out ranges it by a mile. Nasus can't even sit under his turret and farm, because Gragas can roll barrels in from outside turret range.