Anyone who has played team PvP knows that target focusing and communication is one of the most important aspects to victory. Vice versa, surviving when you are the focus fired player is just as important.
Most of the evasion skills for each class are equivalent in terms of closing or creating distance between you and your enemy. One key difference between smoke screen and everything else is that with the other skills if you escape the opposing team can still choose to continue targeting you using either ranged classes or using their distance closing skills to match yours.
Smoke screen (runed indigo) should completely nullify you as a potential target, force the other team to change retarget, and for melee classes to close the distance to the new target. This process can take awhile, and can be the difference between winning and losing. It may even make smart teams put Demon Hunters very low on the priority list because they know they can't count on killing them.
Big Assumption: You will be completely invisible to opposition.