DS for a trapsin in questing gear typically has a radius of 13+ yards, enough to cover the entire 800x600 screen. The HF aura can hardly have a negative effect on how it searches for corpses to explode. they never explode slowed targets - only corpses, and nothing can slow corpses down ;-). With 2 separate DS traps, you can hardly kill (other than by using psn) monsters outside the area that the 2 DS have covered, because they are just too far away.
Defense is useful to shadow/merc/others, but useless to the trapsin herself. On HCL, my untwinked trapsin solo'ed entire Hell except ancients with ~200 total defense endgame.