The scout is good at recon and harassing the enemy. Frontal attacks are ill advised because of his low HP and damage. Hit&Run tactics are the best way for him to deal with the enemy.
The video shows a player using Stealth to attack an opponent. This is generally not the best use of it. Turns out, enemies usually don't stand around perfectly still just waiting for you to stab them. Stealth is better used in sneaking through enemy defences, to either place a convenient spawn portal, or to drop a Demo pack on a building.
On a second note, the placement of the Electric Eye shown in this video is terrible. Never just place an electric eye out in the open like that. Always look to hide it in grass, behind a rock, in a ditch, etc.
Also when stealthed being hit will take you out of stealth. As a player you can still see stealth only towers and ai cannot see you. So unlike the shapeshifters comparative ability this is really only good for sneaking pass towers and un-observant players.
As a note if you see a cloaked scout attack him with range or whatever so your towers will be able to attack him
if u are stealthed and see a blue ring under you, u can be seen and theres probably a sentry bat nearby so find it.
as for backstab, i think 80% of the time we should call it face stab since thats where it end up going. BEST time to use it is when enemies are attking ur structures, thye tend to bunch up and just run in a nd use it, can take out a few enemies at once before thye get defensive.