Generally, you are screwed. Most soundboard patches you get outside of a large arena are going to sound that way if you're taping a louder band (unless you get a special mix from the sound guy or know how to run multi-tracks).
You can try the following to see if it helps any:
Highlight a section of the recording.
Hit "Effects" on the upper tab, then "Graphic Equalizer"
On the left sight there is a preset for "vocal cut" or something to that effect. Click it.
Now try the preview mode to see what you get. You can try to pull down the midrange levels in the graphic equalizer and/or boost up the low and upper frequencies too. If you hear something you like by trial and error, hit OK.
That said, I still think you're screwed.
Tim