Every assassin should have this passive.
When not seen for (A) amount of time, champion damage is increased by (B). After being seen, champion damage decreases by (C) over (D) amount of time
The entire point of an assassin is not be seen, to sneak up on an enemy, to secure a kill as quickly as possible, and make an immediate escape. Assassins aren't long distance runners. They should never have the ability to chase someone down.
Reward assassins for being skilled in stealthy gameplay. Reward teams that ward jungles. Punish teams that don't ward.
I think this is a major frustration I have with Riots half hearted attempt at champion classes. All they did, really, was create a webpage that said which champions belong in which classes but it is clear the intention has been to have champions blur the line between multiple classes whenever possible. I think this would have made sense if they started down this path in 2011 when there were half as many champions in the game. There are now hundreds of diverse champions to choose from and with the itemization changes over the past two years multiple build paths for every champion. _ Sticking each champion into a single defining class, and uniting each member of that class with a specific defining characteristic will not hinder the dynamic gameplay that Riot is aiming to achieve. Instead, it will provide the structure and clarity that it desperately needs._