I personally do not like the C-rig when surf fishing with grubs..
T-rigging is better, IMO. You wont have to worry about the line fouling itself, and only one knot to tie.. Plus as a Bonus, you can feel ALOT safer around that kelp. Whenever I go surf fishing at newport, I'll T-Rig and go straight into that kelp along the jetties. Lots of huge fish hide around there.
Nothing wrong with your lure being "pinned" to the sand, after all perch and croakers are TRUE bottom feeders! All that sand being stirred up will definitely attract fish, especially croakers.
if your jighead is not performing right, you're using the wrong weight for your line class.
if using 6 lb test, stick to 1/16 oz jigheads, this is PERFECT. A common mistake is choosing 1/8 oz jigs with 6 lb, it's just a LITTLE bit too heavy.
But hey, lots of people slay with C-Rigs, to each his own!