Transferring a Collection using DTO Pattern

I needed to return some JSON for the CMS side of our site. Currently it works like so:

My Controller passes SKUs to a CollectionAssembler, which then gets a product category from my ProductCategory class, and gets the rest of the product information from another model.

The CollectionAssembler uses this data to then create a Product object, which it hands off to the CollectionDTO.

CollectionDTO

<?php

    class Rsc_Ga_Model_CollectionDto extends Mage_Core_Model_Abstract
    { 
        protected $_data;

        public function addProduct($product)
        {
            $this->_data[] = array(
                'sku' => $product->getSku(),
                'name' => $product->getName(),
                'category' => $product->getCategoryString()
            );
        }

        public function serializeProduct()
        {
            return json_encode($this->_data);
        }
    }

My question is, am I employing the DTO/Assembler Patterns correctly? Is it okay to pass a Product to the DTO and have it set data in this way, or is there another Object that should handle this part for me? Is it okay that the Assembler operates by creating an Object?

I feel like I'm stretching the pattern from it's original intent, and so I want to make sure I shouldn't be using something else.