SSDs are often considered farming troops, their high speed and easy training being their biggest points. In PvP, however, they have the boon of being easily replaceable and speed troops.
In full scale elite battles SSD are not much more than speed bumps on the offensive side, but for the defender they can be used for protecting troops. This does not mean SSD should replace ogres, titans or frost giants as a meatshield.
SSD in large enough numbers can easily wipe out lava jaws, venom dwellers and arctic leviathans, and speed troops will target them, which may help to save your valuable ranged troops such as Lava Jaws.
For example, take the image on the left. Using 50k SSD on the wall would not have won the battle for the defender, but it would have made the damage to the VDs or maybe even the ALs much greater. Kills can make the difference in a battle; whoever loses the more valuable troops is hurt more, regardless of whether they won or not. The defender in this case lost ogres, frost giants and lcs; all the other troops were in such small numbers they did not matter so much. The attacker lost lava jaws, venom dwellers, fangs and some ogres, in about an equal amount. In this case the defender and the attacker lost an equal value of troops.
If you view the report on the right, you will see the defender had few losses (total losses are shown) other than his SSD. His melee troops and his sandstriders would have probably been hit very hard by the ruiners if it had not been for the swift strike dragons. One of the biggest advantages SSD have is their speed, which enables them to hti before too much damage is done too them.
SSD should not replace elites, but it is easy and takes a short time to train 20-50k. These will be easily sacrificed troops that could make a considerable difference in an average battle. While by themselves SSD are fluff, they compliment and protect elites, as troops can only hit so many times.