I do not think one should approach it as 'best' for 'class', but rather 'best' for 'purpose'.

What is your purpose?
Are you a healing CNJ or a fighting CNJ?
Are you a party THM or a solo THM ?

Are you a WHM in a controlled party (and thus never run out of MP) or a chaotic party (and thus need all the MP help you can get).

Many different purposes.