Depends on what your interest is. HEre's wat i saw in the places that i did visit.
a) Nami Island - didn't go can't comment
b) Dae Jang Geum - Filming site u mean? Well i was a big fan of the series so for sure must go but it is quite a trip. Interesting to see the key spots that they filmed at but be prewarned the sets look much nicer on film, real life quite shabby d.
c) Lotte World - not a fan of theme parks so didn't go in from outside at the mall(i'm assuming tat's the right one) so, so only.
d) Everland - didn't go.
e) free bus shuttle to Gyeongju - When i went it was spring so the cherry blossoms in full bloom very pretty, also rapeseed flowers. but nov i dunno. got the tombs which to me was eeee oklah.
f) free bus shuttle to Jeonju - didn't go.

hope this helps.

is Busan really worth a visit? i'm thinking of another trip to korea so that caould be added to the itinerary.