Currently the Charm chance and charm duration are incorrect.
On the charm talk page on ffxiclopedia (also stated on main page)
An LS member linked this post from Allakhazam about exp rings but it mentions exping thf/bst to test out the rings as early as oct 2005.Using Charm when BST is set as subjob is affected by your real BST level, not your BST level as a sub.
After reading about people claiming it is true, and people claiming it is false, we decided to test it by ourselves.
A friend and I went to Eastern Altepa Desert as WHM38/BST19 both as Tarutaru and with no equipment at all, so we had exactly the same stats, the only difference was that her BST was level 35 and mine level 74.
Then we start spamming Gauge to some charmeable mobs in the area, Spiders, Beetles and Dhalmels and we found what for us is the prof of the above statement.
Most Even Match and Decent Challenge gave me the message "PLAYER should be able to charm the MOB" while the same monsters gave my friend the message "PLAYER might be able to charm the MOB".
A tough mob was "PLAYER might be able to charm the MOB" for me, and "It would be difficult for PLAYER to charm the MOB" for her.
And that's it. Oviorus 18:51, 9 November 2007 (UTC)
I've combed through allakhazam's beastmaster forums (being one of the few remaining forums with all the old posts still up) and the debate begins very early on but as time progresses forward (still early and in era) the posts begin to reach the consensus that it does work off beastmaster main level.
I also found this blog that mentions soloing as a 30+ war/bst in august 2005