You'll want /nin for your Blue Mage at higher levels anyway.
Same goes with Drk once you party with Dark Knight's around level 65 ish that are putting out good damage.
Red Mage, you will want Ninja at level 75 (only*) for soloing certain NM's.
*It's also usuable at low levels since you'll be able to use two wands with great stat bonuses, will only cost you about 20 mp around level 20.
Your highest job is umm... Warrior level 25? I understand it can frustrate you to feel like you will have to be /ninja for everything. You need to know though, there's many experience you have yet to take playing this game, and you definetely don't want to start out with a genuine hate for Ninja subjob without much valid reasons.
You will want it at some point.
Unless you don't care about your performance on certain things. (Where the issue rises that other people do care.)
Oh and Murphie, be careful on the name calling.
