Definitely. Gutloading simply ups the nutritional value of the insect, but not necessarily the calcium levels, which chameleons are unable to gain naturally, even with their UVB light. Repashy is one of the best calcium supplements. It is extremely important to dust insects prior to feeding. I also on occasion dust the insect's food prior to gut-loading them.
The reason why you want to at least do just a plain calcium, is because crickets have a very poor calcium to phosphorous ratio. In the body, you want phosphorous and calcium to be at equal levels, so your bones and muscles can properly use calcium. But since crickets have 3 times more phosphorous than calcium, you see that you start to get a pretty bad deficiency if you don't correct it.
So when you use plain calcium (no vitamin D and no phosphorous) you ideally bring that ratio back into the favor of balance, and your chameleon will be healthier for it. Ideally, you want to use plain calcium, lightly, at every feeding. Especially if you have any females.
The gutloading will help add vitamins and nutrients to the cricket, but dusting ensures that you're correcting this calcium deficiency in crickets. It's why it's also a great idea to vary your feeders, and use as many different insects as you can.