Example of using the `vc_shortcodes_css_class` to streamline VC's class name output on parent elements. See line #53 `add_filter()` and the `filter_vc_row_class()` function on line 73.

class-custom-vc-element.php

<?php
/**
 * WDS Visual Composer Custom Element
 *
 * @since NEXT
 * @package WDS Visual Composer
 */

/**
 * WDS Visual Composer Custom Element
 *
 * @since NEXT
 */
class WDSVC_Custom_Element {
	/**
	 * Set the element name.
	 *
	 * @var WDS_Visual_Composer
	 */
	private $element_slug = 'wds_cm_vc_custom_element';

	/**
	 * Parent plugin class
	 *
	 * @var   WDS_Visual_Composer
	 * @since NEXT
	 */
	protected $plugin = null;

	/**
	 * Constructor
	 *
	 * @since  NEXT
	 * @param  object $plugin WDS_Visual_Composer $plugin Main plugin object.
	 * @return void
	 */
	public function __construct( $plugin ) {
		$this->plugin = $plugin;
		$this->hooks();
	}

	/**
	 * Initiate our hooks
	 *
	 * @since  NEXT
	 * @return void
	 */
	public function hooks() {
		add_action( 'vc_before_init', array( $this, 'map_to_vc' ) );
		add_action( 'init', array( $this, 'register_shortcode' ) );

		// Filter to replace default css class names for vc_row shortcode and vc_column
		add_filter( 'vc_shortcodes_css_class', array( $this, 'filter_vc_row_class' ), 10, 2 );
	}

	/**
	 * Register a shortcode with WordPress
	 */
	public function register_shortcode() {
		add_shortcode( $this->element_slug, array( $this, 'shortcode_callback' ) );
	}

	/**
	 * Use filter to change CSS class names in output of VC elements.
	 *
	 * @link https://wpbakery.atlassian.net/wiki/display/VC/Change+CSS+Class+Names+in+Output
         * @link https://wpbakery.atlassian.net/wiki/display/VC/vc_shortcodes_css_class
	 * @since NEXT
	 * @param string $class_string Class name.
	 * @param string $tag Tag name.
	 * @return string $class_string
	 */
	public function filter_vc_row_class( $class_string, $tag ) {
		if ( 'vc_row' === $tag  ) {
			$class_string = 'row ' . $this->element_slug; // We add the element slug as class name, as well as .row.
		}
		if ( 'vc_column' === $tag ) {
			$class_string = 'col-sm-12';
		}
		return $class_string; // Important: you should always return modified or original $class_string.
	}

	/**
	 * Register an element with VC.
	 */
	public function map_to_vc() {

		$fields = array(
			array(
				'heading'     => __( 'Featured Class Heading', 'wds-visual-composer' ),
				'description' => __( 'Enter a heading for the featured class. The class name would be perfect here.', 'wds-visual-composer' ),
				'type'        => 'textfield',
				'param_name'  => 'heading',
			),
			array(
				'heading'     => __( 'Featured Class Image', 'wds-visual-composer' ),
				'description' => __( 'Add an image for the featured class.', 'wds-visual-composer' ),
				'type'        => 'attach_image',
				'param_name'  => 'image',
			),
			array(
				'heading'     => __( 'Instructor Name', 'wds-visual-composer' ),
				'description' => __( 'Enter the name of the instructor for the class.', 'wds-visual-composer' ),
				'type'        => 'textfield',
				'param_name'  => 'instructor',
			),
			array(
				'heading'     => __( 'Class Description', 'wds-visual-composer' ),
				'description' => __( 'Enter a description for the cooking class. What will students learn?', 'wds-visual-composer' ),
				'type'        => 'textarea',
				'param_name'  => 'description',
			),
			array(
				'heading'     => __( 'Location Name', 'wds-visual-composer' ),
				'description' => __( 'Enter the name of the location where class will be held.', 'wds-visual-composer' ),
				'type'        => 'textfield',
				'param_name'  => 'location_name',
			),
			array(
				'heading'     => __( 'Location Link', 'wds-visual-composer' ),
				'description' => __( 'Provide a link to location\'s page.', 'wds-visual-composer' ),
				'type'        => 'vc_link',
				'param_name'  => 'location_link',
			),
		);

		// Define the element.
		$params = array(
			'name'            => __( 'WDS Custom Element', 'wds-visual-composer' ),
			'base'            => $this->element_slug,
			'class'           => $this->element_slug,
			'category'        => array( __( 'Content', 'wds-visual-composer' ), __( 'WDS', 'wds-visual-composer' ) ),
			'params'          => $fields,
			'icon'            => '',
			'is_container'    => false,
		);

		// Register the element with VC.
		vc_map( $params );
	}

	/**
	 * Build the HTML output put for the VC Element.
	 *
	 * @author Damon Cook
	 *
	 * @param  array  $atts    The shortcode atts.
	 * @param  string $content The shortcode content.
	 * @return string          The HTML.
	 */
	public function shortcode_callback( $atts, $content = null ) {

		$atts = shortcode_atts(
			array(
				'image'         => '',
				'heading'       => '',
				'instructor'    => '',
				'description'   => '',
				'location_name' => '',
				'location_link' => '',
			),
			$atts,
			$this->element_slug
		);

		// Build all the links.
		$location_link = vc_build_link( $atts['location_link'] );
		$location_link = $location_link['url'];

		ob_start(); ?>

		<article class="featured-class-card card">

			<?php if ( ! empty( $atts['heading'] ) ) : ?>
				<header class="featured-class-card-header">
					<h2 class="featured-class-card-heading h3"><?php echo esc_html( $atts['heading'] ); ?></h2>
				</header><!-- .featured-class-header -->
			<?php endif; ?> 

			<div class="column-one-half">

				<?php if ( ! empty( $atts['image'] ) ) : ?>
					<?php echo wp_kses_post( wp_get_attachment_image( $atts['image'], 'three-to-four', '', array( 'class' => 'featured-class-image' ) ) ); ?>
				<?php endif; ?>

			</div><!-- .column-one-half -->

			<div class="column-one-half">

				<?php if ( ! empty( $atts['instructor'] ) ) : ?>
					<p class="featured-class-card-instructor instructor"><strong><?php esc_html_e( 'Instructor', 'wds-visual-composer' ); ?>:</strong> <?php echo esc_html( $atts['instructor'] ); ?></p>
				<?php endif; ?>

				<?php if ( ! empty( $atts['description'] ) ) : ?>
					<div class="featured-class-card-description description body-secondary">
						<?php echo esc_html( $atts['description'] ); ?>
					</div>
				<?php endif; ?>
				
				<?php if ( ! empty( $atts['location_link'] && $atts['location_name'] ) ) : ?>
					<div class="featured-class-card-class-locations class-locations">
						<p><?php esc_html_e( 'Happening at', 'wds-visual-composer' ); ?></p>
						<ul class="body-secondary">
							<li><a href="<?php echo esc_url( $atts['location_url'] ); ?>"><?php echo esc_html( $atts['location_name'] ); ?></a></li>
						</ul>
					</div><!-- .featured-class-card-class-locations .class-locations -->
				<?php endif; ?>

			</div><!-- .column-one-half -->

		</article><!-- .featured-class-card -->

		<?php return ob_get_clean();
	}
}

example-output-WITH-filter.html

<div class="row wds_cm_vc_cooking_school_featured_class_single_wide">
    <div class="col-sm-12">
        <div class="vc_column-inner ">
            <div class="wpb_wrapper">
                <!-- Your custom VC element's output... -->
            </div>
        </div>
    </div>
</div>

example-output-WITHOUT-filter.html

<!-- basically, VC's default classes and behavior -->
<div class="vc_row wpb_row vc_row-fluid">
    <div class="wpb_column vc_column_container vc_col-sm-12">
        <div class="vc_column-inner ">
            <div class="wpb_wrapper">
                <!-- Your custom VC element's output... -->
            </div>
        </div>
    </div>
</div>