Ah, yes - you should be using the send pan feature.  Set Guitar 1 to 100% L, and Guitar 2 to 100% R. Remember to set the inputs of your return tracks to DBX L / DBX R respectively.  This will make them mono.  If they're set to DBX S, then that's why it's coming out as hard panned.  Also note the SILENCE bus to avoid the pre-compressed guitar coming out of the mains from the source tracks, and also the post-compressed sound coming out of the mains from the DBX aux track.