I know that there are some champions who are better solo-top than others, such as Shen because he can heal himself and he has good survivability, but what else decides if a champion is primed for solo top? I have seen other champs such as Teemo or Talon do really well in this lane, but I still don't understand the decision.
Most top champions have good sustain,have a way to escape in difficult situations such as ganks, and also has the skill set to be able to defend your Attack Damage Carry and your Ability Power Carry. For example, Nasus has great sustain with his passive, and his w can let him escape out of tough situations. Teemo has the ability to blind and escape. With the blind Teemo can stop basic attack reliant champions (ex. Tryndamere or other Attack Damage Carries) from damaging your allies.