Is divination bugged?

It doubles your light bender orbs, but if you spam attack it only fires 3 or so of them and ignores the rest. The only way to get it to fire all 6 is to massively pace your attacks out by 3s or so, which is a bit tricky and loses some dps.

Most builds I see still take it though, so I was wondering if it's bugged or you just need to work around it?

 

Orbs fire at a set rate, you can't change that, which is why Faster attack speed weapons begin the firing cycle again before the previous one finished. Slower attack speeds help you cast consistently, otherwise you just need to be patient or else you risk having unbalanced health between your orbs.