Singed struggles with instigating team fights (he has W and R but no dashes), so the theory with this build is to work with Singed's kit and giving him a lane that doesn't make you want to slam your **** in the door. Phase Rush gives Singed a huge advantage in lane because it allows you to take short trades, something that's difficult with Conqueror. The Sorcery tree works well with Singed, as Celerity plays off Singed's passive and R, Nimbus Cloak plays off Ghost, Teleport, and Flash, and Waterwalking helps with objective control and roaming. The Domination tree is extremely strong with Singed as in the mid-late game, Singed can heal off many enemies in team fights without the trouble of Conqueror. Phase Rush gets you in, Domination keeps you alive and gets you out.

This build is still experimental. I personally have only 20 games using this build, but from what I can tell it's extremely safe and effective.