How can do double attack in solo arena?

[R218632922]

Hi all,
Just asking since seen this happened from today. Mage attacks in solo arena against me like this. Without skill attack + normal skill attack in same turn.
How can that be possible?

[Atomslaya]

some skills take longer to "cast" than others
for instance delphics take so long to cast that it is possible that your opponent gets a second hit in before your delphic finally hits

[bakuryuuha]

some classes take longer to cast their skills as well.