In my opinion there are several likely factors causing your situation:
1. Tone Knob - Nothing new here many have already said this.
2. Amp - I always thought the Rumble sounded kind of muddy and not very deep. Me and my drummer did a side by side comparison of the Rumble with the JB Markbass and we were amazed at how much deeper AND cleaner the Markbass was compared to the Rumble regardless of various EQ settings (but Markbass cost about twice as much).
3. Playing with 2 guitars and a keyboard. There is no room for you at all UNLESS you go beneath everyone which leads me to my next point.
4. Strings - Just an idea but you may want to try Labella deep talkin bass Flats. Very clean and low sounding and could help you tremendously to stake out your very own sonic space with occasional visitation rights from the Bass drum only (not the keyboard).
5. Pick vs. Fingers - I personally think a pick gives a more defined note vs finger style and having said that I think fingers sound warmer fatter and cleaner with respect to pick click noise (but in a band setting the pick click noise will not really be heard anyways).
6. Limited Freq range - even after fixing all these other issues you still will probably have to stay above the 2nd octave E or F most of the time to really be heard well.
Of course as others have mentioned it could be the recording too.
Do you have an opinion on the Ampeg BA-210 amp? Ampeg: Bass Amp Series - BA-210