I did explain it, you just don't want to listen, you rather act like you're an elitist who's only opinion matters is their own. Line of Sight, the ability to see your target without walls, pillars, structures or other objects hindering your sight. All Range jobs need to see their target to cast at their target. If target rotates around one of the many scattered pillars around the map as well as the path the crystal takes, then the caster can't attack. Or if the cast times are longer than 1 second you can make them fail their casts thus wasting time in the battle thats all about speed and power. Thus gaining a heavy advantage against an enemy range player. I don't know why i had to explain this to an elitist such as yourself.