DISCLAIMER: This is based on the fact that during the course of two hours thieving since the update I have received no higher tiers, and wiki sources haven't been updated yet to contradict the following.
With the Mining and Smithing update came changes to drop tables, so we now see stone spirits in place of ores and bars. This means that Dwarven Traders now drop these stone spirits once pick-pocketed. I have no problem with this.
However, they still only drop rune stone spirits as the highest tiered ore. The value of these are a fraction of the old ore/bar drops.
Given that these are T90 thieving content, would it be possible to see a buff to the drop table? It has been outdated for quite a while now, but this update has given it yet another hit.
Higher tiered stone spirits are an obvious possibility, keeping it within the theme, and keeps access within the skiller-orientated section. Also given that Prifddinas is now the place of choice for most for top tier thieving, there's no need to worry about the market being overly saturated with these spirits.
Another idea/alternative is to include small amounts of currency from other regions. They are traders, after all. Why wouldn't they be selling their wares to the folk on the Eastern Isles? Or perhaps buying ores from the TzHaar?
On a related note, the payments to stop the guards from attacking still require bars as payment. Surely this should be updated to be in line with the new drop table? Not a massive deal, but may effect those who do not have the mining and/or smithing levels to make the payments.