The range at which rengar's warning mark appears yould increase with rengar's movement speed
most of rengars abuses youmus because when they run insanely fast its possible for them to approach their enemies in a way that allows them to jump at their enemy at the very moment that mark appears
either make it so the time for response is equalized across most movement speeds or make rengar's leap slower ... so people will get more time to react to it

= the enemy is now warned from 3k range.