Really?
I find that version of Moriarty every bit as disappointing as Simm's incarnation of The Master.
Now if you want a better version of both look no further than Giancarlo Esposito's masterly performance in Breaking Bad (how does that show keep getting better?).
Both characters should be stone cold evil, their insanity should be shown by rationalising the unforgivable.
They could hire and use someone like Simm and Andrew Scott (as seen on TV), such characters are fun to watch but in the centre of the web, like the centre of a storm there should be a mind that is more differently sane that utterly potty.
More Hannibal Lecter than the Joker.
Dig (is that the correct parlance)?
My Moriarty is Eric Porter, my Master is Derek Jacobi with a dash of Delgado for flare.
Stealing the Mona Lisa and selling perfect copies, handing out lethal plastic spitting daffodils for free to passers by makes chilling sense if you think about it in that 'special way' that makes for good stories but not the best politician or employer.