Here's a revision of Phantasmal Haze to address some of the concerns. Comments on this or the other ideas are always appreciated!
Phantasmal Haze (Wizard, sorcerer and bard spell list)
Illusion cantrip
Casting Time: 1 action
Range: 30 feet
Components: S
Duration: Concentration, up to 1 round
You plant a phantasm within the mind of the target, causing it to see areas more than 5 feet away from itself as shrouded in haze. The target must make a Wisdom save. If it fails, it has disadvantage on attacks against creatures in the haze and on Wisdom (Perception) checks to see within the haze. Creatures in the haze have advantage on attacks against the target and can attempt Stealth (Dexterity) checks to hide from the target. The spell ends if the target takes any damage.
If the target succeeds on its save, the same effects apply but the spell ends the next time that the target’s turn either starts or ends.