Wanted to clarify something for the thread, as its been asked several times and I haven't seen an answer given (this information is being provided for me to share here).
The Stardust Dragon change is complicated and involved a few things, so bear with me.
1. Prefixes weren't working with the Stardust Dragon correctly. So your "Ruthless" Stardust Dragon staff wasn't dealing Ruthless damage, just normal. This is one of the things that was fixed.
2. It was seen that the Stardust Dragon Staff was performing VERY well at "1 minion count" use, possibly too well. As a result, its base damage was decreased.
3. However, the scaling wherein "each additional minion" increases the power of the weapon has been increased. This means that a higher minion count investment is more rewarding than it was before (each minion increase should show a proportionally higher increase in damage than before this version)
The above was made with the consideration of the new prefix damage issue included; by my rough estimates, if you are using a good prefix on your staff, you should expect a SLIGHT decrease in performance on a 1-minion count Dragon compared to the previous versions (in other words, a Dragon being used by a non-Summoner) but by 2 or 3 minion count, the overall damage should come out about the same. Above 3 minion count, you should be seeing an improvement in Stardust Dragon damage compared to previous versions.
I hope that helps clarify things!