Yes, it's changed a lot.
Your overseas license is valid for the duration of your tourist visa (14 days).
After that you need a Dominican license to drive.
American license holders need to take a computer test and driving test.
Plus will be classed as leaners until they take the driving test.
You will need a full license holder with you in order to drive legally within this period.
Most European license holders can have their licenses endorsed by their embassies and do not need to take any tests. Bsically exchange their license for a Dominican one.
I suggest you use the search function to find the 100's of posts on this subject, just type in "license".
e.g
Drivers Licence
Please Clarify - Cars/Insurance/Residency