Don't worry. It's normal. My tablet has it as well. And to reassure you even more.. My LG Optimus G phone has the same. However that one I have tweaked to vibrate more aggressive. I just forgot how I did it. :/ But I reckon you can do the same on the G Pad. It's not faulty, LG just sets the vibration to pretty low..
"XO Pressley has the deck."