I have 3 hirelings at grade 3 - 2 of whom are eligible to bring improvement type materials. The third is enchanting so does not apply.
Generally that means 4 drops a day some, if not most, of which have some sort of improvement materials for that craft.
I have had 2 drops each since the patch and not a single improvement material of any colour, even green.
Granted this is a small sample but given that one of the patch notes explicitly states that it was going to improve the drop rate of these materials I am wondering if possibly, maybe, perhaps it might be that someone made a booboo with whatever values got tweaked?
GM - Malazan
Raid Leader - Hungry Wolves
Legio Mortuum