Sand skills can reveal hidden players, it's been like that for as long I play and as long I know.
Just hide, not cloak.
Dispel, can't remove EDP, it's something they drink and not magically apply.
Chemical Protection skills are also safe from dispell.
If you don't believe me, go to any RO wiki or ragnainfo site and search for it.
Sins overall are too strong, but that also works against them.
Get SP draining items/cards and hit them, they will have to go normal attack/spam berries.
Keep them ranged, trapped, slowed down or whatever.
There are multiple options best is if you use then all.
My hint is thanatos maero card, patience and dragoon warlord.
Coma might do the rest, if not, go reflect.
Barely any sin knows how to play these days anyway, there are some, but those rely on buffs.