I have been reading the official docs and blog posts and SO for hours, certain somewhere the answer would be posted already.. but no luck.
It seems that no amount
As Thariama pointed out, tinymce was not at fault.. but it was my lack of knowing what all CodeIgniter's $config['global_xss_filtering'] = TRUE;
was doing. If you find you are experiencing the same issue, here is how I addressed it; please see here:
Codeigniter - Disable XSS filtering on a post basis .