This is how Ive handled fitting wysiwyg editors height to its content, with a fallback to a min height.
if ( typeof acf !== 'undefined' ) {
acf.add_action( 'wysiwyg_tinymce_init', function( ed, id, mceInit, $field ) {
// set height of wysiwyg on frontend
var minHeight = 200;
var mceHeight = $( ed.iframeElement ).contents().find( 'html' ).height() || minHeight;
if ( mceHeight < minHeight ) {
mceHeight = minHeight;
}
$( ed.iframeElement ).css( 'height', mceHeight );
} );
}