Double drop not turned on?

The original 2x drop doubled the drop chance of meso, so if a monster had a 40% chance of dropping meso, it would turn into 80% chance.
The CS 2x doubled the amount of the drop instead. That way they could stack together.

Nexon has had 2x drop events where 2x drop operated in either one or the other way. Check how often you're getting meso from monsters. If it's 80% or higher, it's 2x.

Some mobs have over a 50% drop rate for ect drops but they are not dropping 100% of the time and thus I conclude that it is not 2x drop