I think this list works really well too. I wouldn't worry too much about the loss of the Harlies... the Yncarne, the Harlie jetbikes and the Black Guardians all synergize well the Scorpions. They'll all be operating at the same range by the end of Turn 2.
I do think however you could perhaps drop one of the Warwalkers and try and squeeze an Autarch in to guarantee you get those Guardians on turn 1 or 2 (not sure if you have enough of them for T1 deepstrike). I think it would add a lot to your Turn 2 counter-punch with the Yncarne, Scorpions and Harlie Jetbikes. Because you can really land a turn 2 knock-out blow, if you can get the Scorpions, Yncarne, Harlies, War Walkers, and all those Guardians to attack as one right in your opponents DZ.
Plus, it would allow you to Reserve everything if you needed to (except Scorpions, Spiders)
and then get them all to reliably turn up Turn 2.
But you know me, I'm an Autarch guy... but I think he just adds so much. Give him a mask, lance, a fusion gun, stick him with the Harlies and away you go. He's really cheap even with all that wargear and just adds so much in terms of early game flexibility and coordinating your efforts. Plus nothing is more fun than dodging a Space Marine player's crazy alpha strike and then delivering a knockout counter punch.