Yes - Adding custom classes to a div.mailpoet_paragraph does not make any sense at all - it should always be added to the element itself (i.e. input element). I had to implement a custom filter in my theme to remove all inline style and add custom classes with regex.

Good idea! I've upvoted it. Would you mind taking a look at my feature request for a Campaign tab and consider upvoting it, as well?

Thanks!