Champions with a lot of HP; Volibear, ROA rushed Singed, Renekton, Cho, etc..
Because turrets does quite low damage, that makes diving not much a problem.
Like some other said, if turrets would do % HP damage, some mid-late game balance problems can be solved. And we can see some other champions picked other than regular 15 champ.
You dont really have much to do when a Voli, Singed, Wukong dives you even after 15 minute mark.
What makes Voli, Singed and Darius good is, instead of having gap closer, they pick you inside their team.