The very latest update should make a bit of a difference. There should be no more "ship not found" errors on the Merchant 2 encounter and DirectSail encounters should be more varied as well.I really can not answer any of those questions as I have not seen anything different from a month ago.
Pirates use only specific pirate encounters now, so none of the regular nations' encounter sets anymore.
This means that you should never be able to encounter a pirate "battle fleet", which was possible before.
It should now only be "warships", "small craft" or "a rag-tag bunch" for the pirates.
I'm hoping that the changes made will help with more varied encounters as well, so that you won't be seeing the same ship several times in the same encounter anymore.
Might still happen, but hopefully less often at least.
A treasure fleet should always belong to Spain and consist of:How would one know when they encounter a treasure fleet?
Between 2-4 trade ships of tier 3
Between 2-6 escort ships between tiers 1 and 4
If you encounter them on the worldmap, the description from your look-out will be "a convoy".
As per the latest update, it should be possible to encounter them in DirectSail too, but of course there is no message from your look-out then.
However, there IS a note made in compile.log, which you can check during the game if you use windowed mode.