Make Lethality Items mutually exclusive
And re balance all 3 for their specific purpose:
Ghost blade: Chase down targets, have move speed and attack speed again (Medium cool down) Dusk blade: for a big one off assassination ( Long cool down) Edge of Night: Smart engages for reaching enemy back line. (Medium cool down)
You may only purchase one. This make's Assassins feel good about having to make a unique choice for each game, without worrying about everyone abusing all 3 items at once.