ISP: Telecom Italia
Type of Internet Connection: Fiber
Internet Connection Speed: 30Mbit/s
Date & Time: 6/30/2015 @ 19:00 GMT+2
Frequency: Always
Character Name: Selnia Vicker
Race: Au Ra Female
World: Moogle
Class/Level: Dark Knight 60
Area and Coordinates: Everywhere
Party or Solo: Both
NPC Name: None
Monster Name: None
In-Game Time: Any

Can confirm the above bugs:
1. Casting Dark Passenger under the effect of Dark Arts only applies the added effect on the monster you're attacking, other monsters will receive non-boosted Dark Passenger damage and no Blind effect is applied.
2. Casting Abyssal Drain under the effect of Dark Arts only gives back health from 1 enemy, other enemies only take damage without giving back health.