So I like your idea, I run Decapitation strike myself, though at 2500 points. I feel at 2000 I don't get my toys

I will always advocate for an infiltrating transport (the
USR transfers when the vehicle is purchased dedicated) so your MD need a ride. Go dozer + multi melta for a 55 opint insurance policy that will threaten a vehicle or 2 wound terminator and gets to 1)infiltrate 2)scout and 3) drive 6" turn one, MD get out and hose something down with rending twin-linked flamers. EPIC. Now, this requires something on the board turn 1 to open up a box (spartan, land raider, etc). I have been favoring 2 quad mortars with shatter shells and a lascannon heavy support squad (5 dudes, sarge arty & augury scanner) with an attached siege breaker for tank hunter. I have 1-shot NON flare shielded spartans top of 1...kinda lame for you opponent but it makes me smile a touch
I also prefer the lightning over the xiphon, but I love the xiphon model, so don't blame you there. It really isn't a bad flyer, it just isn't
AS good at tank hunting as a lightning can be with krackens and BS5 + tank hunter.
I think you are headed in the right direction, just make a couple tweaks. If you want to infiltrate a
tac squad, bump it to 20, buy extra combat blades and take a chaplain with boarding shield and an apothecary to make your opponents real mad
lol
Ok, last point I am getting wordy here, ALWAYS take cameoline on your
HQ's. Maun CAN take it, as there is no rule for named characters NOT being able to take unique wargear in 30k. So now your infiltrated
tac squad in ruins has a 3+ versus that stupid phosphex that will rain down on them.
Any more questions ask boss -
RG is my 30k jam so I'm always down to talk. If you want more strategy, let me know and I'll
PM you a blog, I don't think I can plug it due to dakka policy.