So I was dicking around and making a bass in Synthmaster (not a whole lot of people use it) and I think one of the tricks to getting that sorta "wruahh" tone is to have the modulator you're FMing with (Massive's Phase OSC is essentially just an Sine Wave FM oscilating whatever wavetable you select) set two octaves below the courier. In the above example I quickly farted out, the 1st has has the modulator at the same octave as the courier, the 2nd with the modulator -12st (1 octave) below, and the third with the modulator -24st (2 octaves) below. (I know this example still isn't really the kind of tone you're trying to get at but I think it's a matter of choosing another wavetable)
You could try setting your first oscillator -24, +12, +24 or pretty much any other octave interval and playing the MIDI at different octaves to see if you get any closer to that "wruahh"
