Personally I would swap Dragons for Reapers - at just 750pts you shouldn't have to worry about heavy-armoured vehicles and your scat lasers should be able to glance anything to death, so there's no need really, while long-range infantry might come in handy against Tau or when thinning out Ork/Cultist mobs.
I've seen people bring a Heldrake for a 1000pts tournament, so that's something to bear in mind - if you drop the Serpent and a Warp Spider you will be able to fit in your Crimson Hunter, which can later on fulfill the double role of character-hunter or objective-sweeper. If you know the lists that you might encounter (eg. you've played with those people before) then you'll know whether to expect any flyers or not.
Food for thought: you don't really have any shuriken weapons, which seems a shame seeing how good they are - last Saturday my Guardians easily managed to wipe out a squad of Grey Knight Terminators thanks to those 6s to Wound. Guardians are as cheap as dirt, so they're definitely worth considering, although if you don't want to drop your Aspect Host it might be hard to fit them it. However, another thing that you can do is drop either Hawks or Spiders (they have a similar role of fast, hard-hitting infantry after all) and put Dire Avengers in that place. With a dedicated Wave Serpent they are definitely mobile enough, their extended range (as compared to Guardians) plus Battle Focus means that practically speaking they can outrange a bolter and, being an Aspect, they still benefit from +1 BS and Shrinekeepers.
As far as the Farseer is concerned I tend to go for pure Runes of Fate - the Primaris is super useful and while you might get some powers that are more offensive that "buff-centred", like Mind War, those can still be very useful. But if you want to go pure support on him then probably a roll on Fate would be good and then you either swap the power for the Primaris if it's not good enough (Mind War/Eldritch Storm) or roll once again if tou get a good one (Fortune/Doom). Then you can roll on Divination and swap for the Primaris if need be. Generally speaking I feel that Runes of Fate are quite well-balanced and tailored to what you usually want to achieve with your army (maybe with the exception of Executioner).
And with Warlord Traits... they're randomly generated, so there's no way to plan for that, right?