I feel magistrates are a "somewhere to put specialists if you have nothing else for them to do" class, so I think it does not matter that there are not so many slots later in the game, when you are unlikely to be using them anyway.
Only producing 66% of the GPP the other specialists do, and producing less benifit than most others, is coupled with a great person who produces a fraction of the beakers when used to bulb, is rubbish when settled and whos special ability, while in some circumstances could be vital (ending a war that you are loosing) but I have never used, generally adds up to a rubbish specialist type.
We should definitely fix Magistrate so that it is equal to the other specialist types in GPP. Otherwise, it is equal to other specialists: Magistrate is +1 commerce/+3 espionage, Spy is +4 espionage, Artist is +4 culture. The points are about equal.
For Great Diplomat bulbing, there is a digit missing. There is a stat <iBaseDiscover> that covers the science provided when bulbing. In BTS, this value is 1000 for most Great Persons and 1500 for Great Scientists. In AND, those values are multiplied by 10, but Great Diplomat was not updated. It's an easy fix to make.
Settled Great Diplomats could also use an upgrade. I think having Great Diplomat should be +4 commerce/+6 espionage.
Does this sound good?