As I’ve seen from iRO:
If your target is Goblin, any monster called “Goblin” will count toward the mission (All 5 “Goblin”s will count, but not Goblin Steamrider).
Many players from various servers running *athena forks get problems with their Taekwon. The problem arises when their Taekwon Mission target is a mob whose name is having multiple occurrences in the mob database(Goblin, Kobold, Dimik,Venatu,etc). This mod gives you the option to make it work like iRO(Goblin only), or apply it to all mobs with the same name.
Ref: http://irowiki.org/classic/Taekwon_Mission
Enjoy!