Where am I missing, I have checked every island and have found no other Templar missions available?
No you didn't. There's one on Cayman Sound.
http://www.ign.com/wikis/assassins-creed-4-black-flag/Templar_Hunt_-_Opia_Apito --- It's over idiot. You're going to die here now and the last words out of your mouth will have been.... Poop train. ~ Krieg