Is it worth to develop a vizier's talents when he got 12 or 13 ?

My lowest vizier is now extremely high level. I stuck to developing him.

There is no right or wrong way but whilst you wait for a higher bodies it is best to keep working on the one you have to rank them up.

Send them to the teaching library. !

Focus your money to build up the vizier, use your badges. They level up quite quickly.

If you choose to wait then you need to expect to drop behind which is kind of disheartening.