So I'm curious, what is everyone's opinion on which DPS class is the most complex and/or difficult to play to maximum potential? I've been told that MNK might be it, but I'd like to hear a few more opinions on this.

I only have higher level experience with BLM, and they seem to be fairly straightforward. Fire 1 spam with firestarter proc, then blizzard 3 for mp, then back to fire spam, with occasional thunder usage. I'm looking for something a little more involved than that.