First off, if you're not sure it doesn't have Wasting Disease, don't eat it.
Venison is super lean. It's dry because it has little fat to help keep it moist. The steaks would have to be cooked rare to be moist without additional tweaking.
Most hunters I know do jerky and sausage with the meat as it's pleasant to eat in those forms and fairly safe. I like these forms of venison, but it's not particularly true to the meat.
Another hunter friend of mine takes the tenderloin in small pieces. A long marinade in buttermilk, salt, pepper, and herbs/spices (Rosemary, a little sage) to remove some gaminess. The buttermilk does most of the work, the rosemary adds a little flavor. Wrap in fatty bacon and grill to medium. The bacon helps protect it from drying out and adds fat. I prefer this treatment as I find venison fairly livery when cooked plain.
If you want to do steaks in a plainer fashion, a brine would help with the moisture. In a brine, salt denatures the protien creating a web of sorts to hold the extra moisture IN the meat. Brines usually include added sugar to balance the salt flavor. For a steak, a quick brine is probably best. This is usually along the lines of 1/2 cup coarse (kosher) salt, 1/4 cup sugar and 1 quart water. If you're using table salt, use only 1/4 cup table salt. Stir to dissolve. They dissolve better in warm water, but you should chill it before using it to brine. Keep the meat refrigerated while brining.
I've seen venison for roasting once at a friends, but never had it. He had it in a lengthy red wine marinade. ALL my current hunter friends make sausage and jerky from these cuts. But my recommendations would be to add fat. Not just wrapping the roast in fatty bacon, but actually threading strips of pork fat through the roast, normally done with a larding needle.
I've not cooked a venison roast, but this is the approach I'd take. This is only an educated guess so it might not turn out any better than your efforts.
Thread it with fat and wrap in bacon. Tie it to hold the bacon in place. Braise it a long time at a medium-lowish heat and let the internal temp come up to about 190. You're looking to break down the collagen in the meat to make it moist and tender. This starts to happen at about 180. The meat will hang out at this temp for a while, often called a plateau, and then start to rise in temp again in a more normal fashion. Let it rest at least 20 minutes covered after you take it out of the oven before carving.
Hope you find some help in the above.