Your HOX is not faulty. The pixel grid are normal. In some it is more visible and some not much visible. But, IT IS there.
Few have mentioned like here
that the warmer screen have more visible pixels grids than a colder screen. may be you have a colder one like me and i do have visible grids but, at an angle when the screen is not lit.
Current Devices : LG G2 32GB LTE & Samsung XE700T1C with Windows 8.1
Future Device: HTC ONE (2014) ???...
Few Previous Devices: ..., Imate Jam, KJam, TyTN, TYTNII, Blacstone, Desire HD, HD2, Optimus 2X, HTC 3D, Moto Atrix, Xpera Arc, Incredible S, SGS II, Sensation, SGS II, Amaze, SG Note,...etc (Random order- Not in actual owned sequence