Adding the hook ‘vc_before_init’ inside a object

I found the solution…
First I thought the problem had something to do with wrapping the hook inside a class.. But after some more testing (sometimes you need to take a step back), it appears the hook vc_before_init has already fired on the init hook with the (default) priority of 10…

My current theme (Salient) has made a custom Visual Composer, that is provided in the theme package.. After checking the theme hooks with ‘Prioritize Hooks’ plugin. I found that the theme has the following:
add_action( 'init', 'add_nectar_to_vc', 5 );

I now use add_action( 'init', array( 'WPWDtools', 'run' ), 4 ); to start-up my plugin, and now everything works as expected.

Without diving into my theme any further, I suspect that it forces the vc_before_init hook to fire early (on ‘init’ with priority:5).

I want to thank @phatskat & @gmazzap for helping me. You guys where wright, telling me the hook probably already fired.