Considering the outcome of Macbeth, does Shakespeare view evil as stronger than the forces of good?
If you consider the outcome of Macbeth, the answer is simple. Good is more powerful than evil; and I only say this because, in the end, justice is served. Macbeth and Lady Macbeth are dead and Malcolm reclaims the right to the throne, which was stolen when Macbeth killed Duncan. As appalling as Macbeth’s deeds are, the fact that he is constantly conflicted shows that there was some good in him. The witches did not command Macbeth what to do; they vaguely suggested prophecies which, interpreted the way Macbeth interpreted them, required evil deeds on his part. His own ambition, his wife’s and his interpretation of the vague premonitions of the witches led him to commit an act of evil (killing Duncan). Macbeth became basically mad as he confused his guilt for fear of losing his power. Macbeth’s actions manifest evil and each evil act is his own misinterpretation; that is, each death is his attempt to stop killing (if he kills every threat to his throne, he won’t have to kill anymore). Is it evil incarnate or Macbeth’s mad ambition? Probably both. But in direct answer to your question, the play is about manifestations of good and evil. In that sense, abstract evil and abstract good are equally powerful in their potential. How people/characters act determines the battle between the two. So, the score between evil and good has a lot more to do with free will and conscience of the actors. But in the context of the play: Since the play begins with Macbeth fighting to defend the king and virtuously succeeding and ends with Macduff fighting to defend the rightful king (Malcolm) and virtuously succeeding, the implication is that good is more powerful. At least in this case, in the context of the entire play (not just an analysis of Macbeth himself), everything is restored to its rightful place.
This is purely subjective, but I would argue that Shakespeare viewed good and evil as equal forces that would universally be at war with one another. While Macbeth and Lady Macbeth succumb to the "evil" flaw of unbridled ambition for power, Macbeth is not wholly evil, and goodness (or order) is restored upon Malcolm ascent to the throne.
Similarly, if one looks at any of Shakespeare's tragedies or some of his more meaningful comedies like The Merchant of Venice, order and goodness prevail in the plays' final acts. During Julius Caesar's conclusion, Antony praises Brutus's nobility (his goodness) even though he conspired to kill Caesar and fought against Antony. Likewise, Othello concludes with the hero asking to be remember for his admirable qualities (which are numerous) rather than his flaw of trusting the wrong person. Cassio who is primarily blameless throughout the play assumes command, and Cyprus can once again be orderly.