Sett works more like a support than a bruiser.

People keep building him full damage then falling off hard and not grouping, and will insist on going full damage and will not EVER let someone support Sett because "thats a waste". What is a waste is when someone has a pretty good idea of how to play him and what his more optimal build is likely to be, but is unallowed to play him at all because I want to play him in the support role.

Generally, even when first pick, people will ban him on my team. You cant learn how to play with or against someone if you dont ever play against them and when you just want to be a jerk about it.

Build him almost like you would a damage mundo and enjoy the carnage.