First of all, many guys have had good results with Deca only cycle, also, quite a few others have experienced difficulties with that cycle from progestronic activity and absence of test. Typically if you were to do a Test only cycle you would either take with an aromatase inhibitor or keep a estrogen blocker like Nolvadex handy or use both. With Deca, though less likely to occur, you can have bad progestronic induced side effects and your only defense is either stacking with Winny or taking RU486. Since RU486 is not readily available to males, Stacking with winny is most commonly suggested. This makes a lot of sense for more reasons than just the ability to help block the effects of progesterone---winny is a Class II AS which makes it very synergistic with an aggressive AR binding AS like Deca. Also, it will help with strength and LBM gains while having something of a hardening effect when part of a stack.
The other AS that makes sense to stack is Test, even in low doses. Your body is going to shut down its natural test production for an extended period on that cycle. This is not just bad for the love life, but test is an important hormone for multiple bodily functions, including some of your brain activity.
Personally, the only stand alone stacks I would do are Test-only or Anavar-only, but that's just my opinion, good luck with your cycle either way.