Why don't Supports and ADCs switch summoners?
considering how supports tend to be ability based and have a huge range, but exhaust has 650, lower than most abilities but higher than nearly all auto attack ranges.
Heal gives supports a lot more power when roaming while ADCs who have a trigger happy finger on the flash button can instead use it on their exhaust button as assassins are a lot less powerful when they lose 40% damage unless they wait out the entire thing (trust me, it's not really burst but slowly-deflating instead if they delay their combo for so long) while heal's amount isn't very much later on when assassins start focusing the ADC when they meet in team fights (though 40% will always scale with the enemy's power). Also, ADCs get lifesteal but phantom dancer, IBG and frozen mallet are among the only items to copy Exhaust's effects.