We could make this a lot simpler. How about this?

```js
"VariableDeclaration": function(node) {
    node.declarations.reduce(function(memo, decl) {
        if(!memo) return;
        if(decl.id.name < memo.id.name) {
            context.report(decl, "Variables within the same declaration block should be sorted alphabetically");
        } else {
            return decl;
        }
    }, node.declarations[0]);
}
```