Grounding audio circuit for RFI immunity
1 gets my vote (With some modifications). 

The input arrangement is just fine (Might benefit from some ferrite common mode choke, but...), and is pretty much best practise for RFI suppression on a balanced line. It adds a few hundred pF differential mode (Irrelevant at the sorts of impedances balanced lines run in pro audio) and about 45pF common mode which keep the common mode impedance usefully high in the audio and low ultrasonic while ensuring good line balance (because the 47pF cap swamps the tolerances of the 470pF caps). 
It does however still shunt RF to ground but you will absolutely want to minimise trace lengths in this area, small SMT C0G ceramics are good and if you use an XLR with built in pin 1 bond to chassis (You should), take advantage of it to minimise the loop area inside the box. 

Now lets talk about the output stage.... What you have is more then a little weird, an RLC filter where the pole frequency depends upon the load impedance, and coming out single ended at that? 

If you don't really need two poles here, why not lowpass with a cap across R1? then you can build out with a far more reasonable 100 ohms or so, no inductor (or a ferrite bead to help keep RF out of the doings), and you can impedance balance the output. 







simulate this circuit &ndash; Schematic created using CircuitLab

C1 sets the lowpass pole, trim to taste. 

The internal 0V plane needs to be connected to chassis earth at some point, but it is critical that this not share any net with the RFI or cable screen connections as doing so will create a common impedance that can couple noise into the circuit. For this reason I have shown this connection as a separate bond. 

C4,C5 should be non polar and rated for at least 50V to ensure phantom power is a non problem, and D1,D2 exist to clamp any phantom power accidents (I would not suggest 4148s in practise, pick something modern in a SOT23). 

L1,L2 are ferrite beads (or ideally a small ferrite common mode choke), just more measures to keep the cell phones out, and that '081 should really be a 5532 or such (Something like L1,L2 is not a bad idea at each input as well). 

R4,R5 should be closely matched as they set the line balance and hence impact the CMRR of a downstream balanced receiver, 0.1% parts are not the expense they once were. 

Incidentally, R1,2,3 are lower then I would prefer in a line level application, the extra current flow will tend to raise distortion at high level, a few k is more reasonable (Maybe 4k7?).