Get it to around 43% without hide. If you have stealth, then you can go as low as 41% without hide and stealth toggled on.
Your character does not have capped defense. Depending on your AT the cap is between 175% - 225%. Your defense is not teal in the combat window, it can go higher. STOP SAYING IT IS CAPPED! The correct term is Soft Cap.
I enjoy playing in Mids. I specialize in Melee Characters, other AT's usually bore me.
Yes, you definitely want to get some Def slotted in there. For my NB/Nin, I
looked at positional (Melee, AoE and Ranged) rather than typed.
The goal of course is to get as close to the 45% softcap as you can, but
DON'T gimp your core power attributes (Acc, Dmg) to do it.
For Melee, you can go easier if you slot Divine Avalanche for Acc and Rch.
You can easily double stack that which will give you 30% Def from that alone.
That would let you get away with as little as 15% (but 20+ is better in case
you whiff on a DA)
AoE pretty much happens all by itself with Hide, and personally, that's about
the only time I worry about it - an AoE interrupting AS is irritating... 
Most other times, not so much as they're generally weaker attacks.
Ranged is harder to get, and may be more of a worry (or not) depending on
your playstyle (I tend to take "purely ranged" guys out first, because I
know I can deal with the melee guys using DA, Placate, etc.).
Hope that helps.
Regards,
4
I've been rich, and I've been poor. Rich is definitely better.
Light is faster than sound - that's why some people look smart until they speak.
For every seller who leaves the market dirty stinkin' rich,
there's a buyer who leaves the market dirty stinkin' IOed. - Obitus.
I was wondering how I shold slot ninjitsu. It is a mostly def-based set so I was considering slotting a bunch of def sets in it. Am I on the right track here?