actually
there is no reason for april to use level 10 and switching to level 9
Looking at the structure stated above, let's skip to Arrow Vulcan
Meaning Arrow Vulcan has 3000 milliseconds or 3 secs after cast action delay for both levels 10 and 9
and 2000 milliseconds or 2 secs after cast walk delay for all levels
Naturally
Arrow Vulcan Delay is not Affected by Magic Strings but is affected by Cards/Items
and although it could be affected by dex
it is not known if Kiinz Configured the server if Dex should affect delay of skills