This ability is basically a lower-range xerath q-style, except it travels as a projectile. In Kayle's default state, while quite underwhelming its still useful.Do note that it requires channeling to attain max range, effectively disallowing Kayle from autoattacking for the duration - I wanted to slightly shift the focus from her E to her other abilities, although AA's remain a core and defining part of her kit and the playstyle remains completely viable. (more in E)
In Retribution state the ability becomes more interesting, changing into cone-shape and applying blind to enemies hit in the center, effectively supplying a strong area of damage spell to Kayle and allowing her and her allies to survive longer by preventing the enemies from hitting their autoattacks.
In Hope state an additional effect of cleanse is added. Do note that the ability also "passes through" Kayle herself, effectively removing most CC or DOT from her (even if she only manages to start casting it right before it hits, as the ability will still be released (unless its a silence). It also requires thinking - do I save that ally or do I hit an enemy with it, which is more beneficial to the team as a whole?
OLD VS NEW:
OLD : 60/110/160/210/260 (+ 100% bonus AD) (+ 60% AP) Damage (single target, point and click),slows,650 range,8s CD
NEW(at 0 Faith) : 60/100/140/180/220 (+80% bonus AD) (+50% AP) (line skillshot), 350-600 range,10s CD
NEW(at <0 Faith) : 90/150/210/270/330 (+120% bonus AD) (+75% AP) (cone skillshot),blinds, 350-600 range,10s CD
NEW(at >1 Faith) : 60/100/140/180/220 (+80% bonus AD) (+50% AP) (line skillshot),cleanses, 350-600 range,10s CD
As you can see, the "basic" version is a nerf - longer cooldown, doesnt slow and has to hit, while also dealing lower damage and requiring channeling to maximize its potential.The only advantage it has is in being able to hit multiple opponents but the line is quite narrow (taric-stun like).
In Retribution state the ability changes, becoming offensively better than the old one but still lacking range, the slow and having higher cooldown, which is made up for by its aoe and blind potential and also the fact that a teammate has to die for Kayle to use it
state the ability gains a cleanse component and can potentially save an ally or Kayle herself.