Wait, why would Sash matter? Mega Kangaskhan hits twice.
Slavandar, if your big problem is Fighting-types, Mega Blaziken probably isn't the answer; it's not the sort of Pokemon you want to switch into a Close Combat. Ultimately, Doubles is about getting KOs while not getting KO'd yourself (well, all of Pokemon is like that, but anyway). You want your leads to be killing things so your back-ups don't have to do as much work. I'm not really seeing how this team accomplishes that. You lead with two Pokemon who have 4x weaknesses (relatively common ones too), one of them is slow, and neither of them hits all that hard without a turn of set-up (Garchomp hits hard, but not "KO two Pokemon who take neutral damage from Earthquake" hard). If your opponent leads with something with a strong Ice-type move that isn't KO'd be Dragon Claw (and not much is KO'd by Dragon Claw, since it only hits for neutral damage), your only defense is Sand Veil. That's not a position you want to put yourself in. In fact, don't try to use Sand Veil in general. Winning by 20% hax isn't a strategy that will get you too far.
You'll notice the top Doubles streaks that utilize Garchomp all have an EQ-immune partner lead with it, and none of the teams carry any Pokemon that are weak to EQ (in fact, the only one on any of those teams that takes any damage from it is Mega Scizor, who is neutral to it and has better physical defenses than Skarmory). That way, you don't have to incapacitate yourself just to have Garchomp use its only strong move that's super-effective on anything besides Dragon. Gengar is a good option because 1) it's fast, giving it a good chance to either KO something or weaken it so that Garchomp can KO, and 2) it's frail, meaning the AI is more likely to target it with attacks, meaning you can Protect and make them waste their turns and potentially set up Garchomp. Also, don't use Fire Fang. Get something else that can take on Scizor/Ferrothorn and use Rock Slide. FF is just too weak.
I don't like Blaziken in the back, primarily because it can't switch in on much. A cool thing about Aegislash (besides the fact that yours is shiny, of course) is that it can switch in on pretty much everything ever. That said, its EQ weakness is a problem, because you don't want your bulkiest Pokemon to be forced to do nothing just for Garchomp to use EQ safely. The fact that Aegislash is so bulky also makes it more likely that the opponent will gang up on your other Pokemon, which is a problem when Aegislash is too slow to stop them from doing anything about it. You'll probably want something that can switch in on Ice, though; Rotom-W, (Mega) Scizor, maybe even Mega Charizard Y (it doesn't resist Ice, but it does get good SpDef after Mega Evolution and can destroy Water-types with Solar Beam).
If you make the rest of your team better at taking on Fighting-types, I think you'll be a lot happier with Mega Kangaskhan than you are with Blaziken. It OHKOs a LOT with Return (especially if you're Adamant; the added power from Adamant is usually better than the extra speed from Jolly, especially if you run Sucker Punch). Sucker Punch is good at getting KOs on those fast and frail Psychic- and Ghost-types too (Espeon, Alakazam, Gengar, Froslass). Its weaknesses are also really easy to spot too, meaning you can switch it out against Fighting moves. Then you can bring in something like Gyarados; a decently bulky Fighting resist, especially one with Intimidate, can switch in for free, pretty much.
Good luck!
