From what i've read and understand, you have to hit 160 diplomacy and get the atache title to start getting missions from jiro. I did this, i have the title and have 160 dxp. Though he does not show up as a contact for me, has not contacted me about missions and talking to him directly does nothing.
What am i doing wrong to start getting these missions?
FYI, the "Diplomatic Investigations" will not show up in your mission journal. When you reach the appropriate exploration area, there should be a button (bottom right) to access them. (Which means you need to remember or otherwise record where your investigations are when you accept Jiro's "suggestions".)
Basically you accept the mission not via the mission button, but by the Info button. Once accepted the mission isn't listed anywhere, but when you go to the exploration cluster it pops up. I've found that they are time sensitive, so if you wait too long, the mission will go away without an indicator its gone. The investigations are pretty quick, though the travel time to the sectors can be annoying. As to farming DipEx in exploration clusters, that actually goes pretty fast, though one thing I've run into is some missions start as dip style missions, the abruptly add a combat element, half way through. Its grindy, but I've had worse grinds. I've found you can get jiro missions, at least once per hour, possibly more.