Is there a casting delay on some Druid skills, as there is quite noticeably on Sorceress spells?
Yes. For example, you cannot cast Armageddon successively without a lengthy pause. For those concerned about them having been “weakened” during the beta, the casting delay was instituted to reduce graphical overload, but the spells themselves were given upgrades, so they do as much damage as before, they simply do more with fewer castings.