the dual rack is not an ideal solution as they took up spot that can be used for land attach/Anti-ship weapons. The central fuel tank is small anyway and it can be replaced by making the other 2 fuel tanks larger (as on Mirage 2000). If they can do that, it allows J10 to carry 2 fuel tanks, 2-3 PL15, 2 PL10 and 2 large ground/ship attacking weapon without changing the air frame too much.
Dual rack only takes up 1 pylon, so it doesn't take up any additional hardpoint. In addition the J-10 will most likely be rocking three external fuel tanks, much like the Rafale and Eurofighter (heck even the F-15s rocked up with 3 tanks in Southern Watch), to long range/duration operations.
Unlike other countries, the PLA has the luxury of not requiring one fighter to do every job. A fighter that does every job ends up being a jack of all trades but a master of none anyway. The J-10 is a capable air-to-air platform, but if the PLAAF needed to clear up the skies, chances are they'd send in the J-20 (dedicated air superiority fighter) and J-11 (larger missile loadout) instead of the J-10. As for strike, well the J-16 (a dedicated strike fighter that can hold a boat load of bombs and munition) and to a certain extent older JH-7s have a greater striking capability than the J-10.
As such the J-10 primarily serves as a multirole fighter to conduct counterair (basically air patrol), AEW/tanker/mobility escort, fighter sweep, a limited strike mission, and perhaps SEAD (lightweight airframe makes it ideal for dodging SAMs and AAA). That's why there isn't a need for the J-10 to have a truck load of BVR missiles. When the J-10 was designed as a lightweight fighter, more missiles and munitions would only add additional weight and drag, which takes away its advantage/selling point.
Counterair operations, no-fly zone enforcement, and escort loadout:
- 2x PL-10
- 4x PL-15
- 3x External fuel tanks
Anti-ship or strike loadout:
- 2x PL-10
- 2x Precision guided bomb or 2x YJ-9
- 3x External fuel tanks
- Targeting pod
In other words, the J-10C still packs quite the punch and has very impressive capability. Why else do you think all the Pakistani fanboys have been crying for its procurement?