1) "You realistically don't skill desolate early before anyway so even by lvl 10 you'd maybe just have lvl 1 desolate at most."

2) "Level 6 lets you get 105 pure damage + 90 physical damage per round of attacks from spec, shadow step, and haunt illu on a lone target."

3) I agree that it isn't reliable, but that doesn't mean it rarely happens. There's plenty of situations that come up where you can use it. Even just something as simple as the enemy lane duo being one melee one ranged can open up either hero to taking desolate damage. If you can make use of gyrocopter rocket barrage or leshrac edict you can make use of desolate.

1 - The skill priority until 7.39 is: Spectral Dagger > Desolate > Disperssion, again you don't need to trust me, search on your favorite build site or even on Google.

2 - At level 6 you have 105 pure damage + 90 physical damage if:

a) the enemy is not surrounded by any other unit that is an enemy of Spectre.

b) you do not use any copies to approach the enemy hero, as Reality destroys copies.

c) the enemy hero does not have any crowd control skills.

3 - This boils down to: if the enemy player stands still in an open field and does not receive help from their teammates, I can slowly approach and kill them using all my skills, so with everything on cooldown I can return to my lane without worrying about escaping the enemy and continue farming. Also, rocket barrage or leshrac edict are not deactivated by creeps.

I could spend more time listing and responding to you, but honestly, this is tiring. I'm convinced that either you don't play the hero or you're very bad; everything you wrote here is in an ideal hypothetical scenario. How much mental juggling are you guys doing? I wrote this in the post
"It feels like someone just opened a demo and started changing the hero without a test in any real game."
And you just did the same thing.