I'll include the 2 most common designs (the ship was developed in the TIE Fighter PC sim, and used one design shown but was later changed to the other design, and sadly I forget which came first now even) known to the community here.
A quick note on your reference of the ship...
The ship, if I'm recalling correctly, was developed BEFORE the Battle of Endor, as it was first introduced in TIE FIghter which chronologically takes place before Endor. In the game it actually sports quad-lasers, dual Ion cannons, and the dual warhead launchers as well. Pretty heafty payloads if I'm not mistaken also, and shields/armor that rivals most any fighter if not surpass any in service. Nice stuff.
In TIE Fighter, the ship was never much more than prototyped... It made it to production only in limited numbers prior to Endor, and in factories that were remotely located beyond the galaxy's outer rim territories. The TIE Defender was part of a technology development program by Grand Admiral Zaarin that also included the development of cloaking technology for medium sized vessels (which literally blew up in Zaarin's face). Zaarin attempted a coup de tat, but failed as then Vice Admiral Thrawn moved his fleet in to supress the renegade fleet and secure the technology developments.
Zaarin also developed the TIE "Avenger" Advanced fighter which was the new up and coming fighter at the time, and an advancement on the TIE Advanced x1 design used by Vader.
EU clashes at this point, as much of it claims TIE Interceptors weren't in service till AFTER the ANH events, but X-Wing and TIE Fighter deviated and claimed Interceptors to be predecessors to the TIE advanced, and in use long before the Battle of Yavin. That's why there is some discrepency there in what EU claims what.
TIE Fighter says the Advanced x1 (Vader's TIE) then instead lead to a decently shielded, fast, and hyperdrive capable TIE "Avanger" Advanced that was a hybrid of the best attributes of Vader's TIE and the Interceptor. Zaarin's engineers developed the Defender then, as a means of Imperial fighter squads regaining space superiority as the "Avenger" was definitely a good fighter but still matched by better skilled pilots in the Alliance using X and A-Wings.
The Defender, and the ship that never saw full production, the Missle Boat, were to be the fighters that would win the war by turning Alliance tactics against themselves while utilizing the superior financial ability of the Empire to produce a vastly superior fighter in decent #'s, and in a short period of time.
Coincidentally, the X-Wing series also says the A-Wing was a pre-Yavin ship as well as the Interceptor, and now even some EU claims the TIE Bomber was created after Yavin though most EU doesn't lean that way.