The Paladin is clearly entering his "spell animation" when using this. That's a huge red flag if this spell is meant for AoE damage. Having a cast-bar means:

- Spells can be interrupted by damage (When you are the target of 15 mobs that seems counter-productive.)
- Your ability rotation is cancelled (The biggest reason why Clemency is shunned.)
- You can't block or parry while casting
- You can't use it while moving.
- Spells use the same resource as Flash (which already uses up most of your MP on big / continuous pulls.)
- It can't replace Flash if it's not insta-cast.