It's different for everyone. Some people can do Pandora, but flop on the Leno. Some people (myself for example), get murdered on Akira. I can do Mayhem, but I can't do Eko.
None of them are hard, you just need the knack for them. Even if it doesn't show yet, the flourishes you can\can't do are influencing your style--NOT necessarily what you like the look of.
In that respect, no offense, but I think that asking how hard a flourish is and hoping to get a gauge for yourself isn't very viable. I haven't even gotten to Eko yet, so I couldn't give you a rating.
Sun|Sky