Two things that need balanced.

Stormrazor slow is just obnoxious to play against its to good of a first item. Its not the stats its just the slow it provides. The slow mechanic on it stops many champions dead in there tracks because an adc rushed it first. Qss into malz or morde is needed to counter act there abilites but this is item does not follow the same rule. Qss is built to counter specific while stormrazor is working to much as a cover all for adc's.

Sett's regen and true damage makes him able to take super bad trades and then regen health at rates like garen does. While he is a new champ and will see his nerfs in time a lot of these problems could be fixed before they hit the rift. The innate half beast passive really is just a crutch that allows a player to take a bad trade and then just heal up under tower instead of being forced to back. The regen after playing two games into him really just gives him an edge in games because he can mess up his combo take a bad fight but just run back after trading and heal up. I dont mind the champion being overtuned like every newly released champ and he is no where near aphelios level's of busted. Finally the w true damage will just need to be toned down and then the champ will be balanced as possible. the shield is cool but being hit for 436 true damage not so cool.