On their own, each steroid has a unique effect. When you combine them, the effect is greater than either of the individual steroids at a higher dose. Synergy, where 1 + 1 = 3. The issue for you us, orals are not really a safe idea to use as your base. You want to use test as your base, which is far safer than orals. Then if you want to start stacking steroids, you can stack otehr injectables or stack an oral with your test. If you are not comfortable with the idea of using an injectable, you might want to rethink your commitment to usoing gear. Avoiding an injectable because you don't like the idea of them, is irresponable when it comes to your health. Orals can be hard on your liver. We all hear about that online. Even when we use them in moderate doses, we expect liver values to get quite high and expect to have damaging effects. Less often, we hear about the cholesterol effects that orals have on our body. Even Anavar, considered a safe steroid, can and will cause an impact on your cholesterol. The best we can do to keep ourselves safe,is to limit the amount of time we use orals and rely on injects to carry us through our cycles. There is tons of info out there about how to safely do injections with oil based depots. Educate yourself and the fear will be less. Check out juicedmuscle.com. In the steroid learning center, there is a good write up on injections in the sticky section. 

Orals aren't "bad". They can be used effectively. It's just a matter of minimizing the time you are using them and staying with moderate dosing. For someone that is new to gear, sure they can do well with a 6 wk dbol only cycle, but for someone that has been invloved in gear use for any period of time, you need to step it up and think about health. You do not want to be running orals, increasing doses of them and combining them as your sole means of making AAS related progress. If you wanted to combine orals, I would use 1/2 of the effective dose of each. So if you are newer to gear and have done a dbol cycle, then wanted to combine dbol with something else. Something like this could work. Although, it would work way better with test at the base, even if it were only 250mg EW

1-6

Dbol 25mg ED

adex dosed as needed

1-4

Drol 25mg ED

Then after 6 wks PCT would start.