Nitpick: often we refer to "omnidirectional" bass because, given that subwoofers are usually much smaller than bass wavelengths (around 16 ft at 60 Hz), they have an omnidirectional radiating pattern. Live sound is usually highly artifical, with the heavy use of compression, EQ, effects, and a very exagerrated bass. For instance, all reverb is usually digital, because instruments and singers have to be close-miked to…
You still want stage level to be consistent between instruments. Open-back guitar cabinets are less beamy than closed-back cabinets, and have less acoustic suspension fake bass to boot.
Live sound does not have to be particularly artificial at all so long as the venue has decent acoustics. You probably don't need the reverb or compression, and EQ is really only any good as a mixing tool.