I have yet to test out the latest update, due to not wanting to break anything further, but from the looks of it, the latest version of ACF should have resolved the issue.
Since I really needed a fix, the day I posted on this thread, I decided to use TinyMCE Advanced ( via http://wordpress.org/plugins/tinymce-advanced/ ) as a work around to the issue stated above.
TinyMCE brings back the WYSIWYG options that are removed.
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Download Latest Version: ACF 4.3.8 http://downloads.wordpress.org/plugin/advanced-custom-fields.zip
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ACF Change Log as of 05.07.2014
4.3.8
Validation: Fixed disabled button issue in WP 3.9
4.3.7
WYSIWYG field: Fixed missing tinyMCE buttons in WP 3.9
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