The following rule is working fine for me in conjunction with your other rules:
Code:
{
"enabled": true,
"logging": false,
"maxDecryptDepth": 1,
"name": "dpreview.com find single galleries links inside gallery category",
"pattern": "https?://www\\.dpreview\\.com/sample-galleries\\?category=cameras",
"rule": "DEEPDECRYPT",
"packageNamePattern": null,
"deepPattern": "(https?://www.dpreview\\.com/sample-galleries/[0-9]+/[a-z0-9\\-]+/[0-9]+)"
}