Scout is lacking. First I curse everytime he is picked. He is mostly useless for the team but very good at stealing kills while avoiding being killed with stealth which makes him the ultimate statwhore hero.

First his Vanish needs balancing: He can constantly use it without any mana problem as the cost is low and then it has more duration than cooldown, which means he can constantly stealth backstab and restealth without ever getting into mana trouble. Balancing is required in not making the duration as long as the cooldown OR increasing the mana cost to stop the "spamming" and make him visible for short time while restealthing so he has to watch his positioning at least OR add a cooldown to stealth AFTER he did backstab.
Right now he steals "Night Hound"s USP by being perma stealthed.

And second he blows. He is like useless for the team. He has not the hunting skills and anti stealth of a bounty hunter and his only good team skill -- the wards -- have long cooldown and arent that great. MY suggestion is to change the observer wards into an "Utility" skill. Like Soulstealers 3 nukes he also gets 3 buttons which grant different skills.
First button: Eye
Second button: Alchemic Bundle (invis)
Third button: Detonate!
The green demo pack from Savage 2 makes a comeback on the scout. You can place it and make it explode via button. This would balance his Vanish-Nerf and make him more viable as team hero and not just a useless killstealing starwhore hero. Instead of Detonate which would fit in nicely on his ultimate to catch running heroes if it is well placed*, he could also get a third utility skill and make demo pack detonate after some time. Sadly I cannot think of a third utility skill based on Savage1/2.

*Example, you place it between 2 towers on a lane and once you get a hero low and he is running away, you can finish him off using the pack.

What do you think?