I'd say you have some problems with tuning and shot placement. I too am a lefty and shot a righthand PSE for two years. I found that with a little practice I was grouping just fine (also leard that tight groups are expensive when you slice off fletching) Folks who are right handed didn't grow up having to adapt to the right handed world and sometimes think different is wrong. I now have a lefty Hoyt and think it shoots far batter when everything is on the correct side.

Get a NEW bow that FITS! Get it tuned by someone who takes pride in his work and then shoot it plenty. Take whatever measures it takes to reduce noise too. A deer can cover enough ground when he hears the arrow release to make a perfect shot hit the hindquarter.

Then study the layout of deer vitals. The 3-D targets you see at the store have the parts in the wrong place most of the time. A slight quartering away shot placed toward the rear of the ribcage will dispatch a deer quickly.

Just my thoughts