Varus' Passive. An idea.
Edit 2: Note that numbers might always be subject to chance, or can be scaled by level. I chose relatively high values since compared to other carries he lacks strong steroids and the new passive only applies near towers. Not in jungle fights. Please rate the idea rather than the numbers
Edit 3: Values at allied towers lowered. Values at enemy towers now scale per level.
Varus lore summary: Varus is a Guardian who failed to defend his temple. He allowed himself to be corrupted in order to seek revenge.
Varus' Passive (current): 20% asp for a CS. 40% for a kill or assist foe a short timeframe. Issue: It's not a strong effect and it only triggers if your team is already ahead in the fight.
Varus' Passive (suggested): Near an allied tower (800 range) Varus gains increased auto attack range( 825 total attack range). Near an enemy tower (800 range) Varus attackspeed is increased by 14 + 2*level %
Explanation: The suggested change fits Varus lore, as a Guardian he gains range to defend allied structures, while near enemy structures he gets consumed by his rage making him attack much faster in his frenzy. This passive does not help him in jungle fights, but really makes him a great "guardian" for your turrets. The additional range and his ultimate make diving very difficult for enemies, while his Q and passive allow sieging enemy turrets very well. His weakness shows during Baron, Dragon, Blue or Red fights which don't take place near towers. (They're just monsters, they didn't attack his temple. There is no reason for him to stir up his rage or guardian instincts)
I believe that the above suggestion not only fits his lore well, but also grants him a unique nieche.
Edit: I'ld suggest to add a blue glow while he is defending structures and a violet glow while he is attacking them, possibly varying in intensity depending how close he is to leaving the range.