the major threats to this team are the lati twins, gengar, and breloom; hazards can be played around but have the potential to really give you a hard time, especially if it's deo-d who's setting them up. i think defensive starmie could potentially work wonders on this team, probably over latias since it can fill a similar role in checking keldeo; it can spin with ease and it psyshocks gengar/breloom to the grave. switching it in is a bit of a tricky dance, but it can be done with smart play. also, an advantage starmie has over latias is the ability to ward off pursuiters with scald burns.
the lati twins are still an issue, but you can play around them with genesect; terrakion/gothitelle can also check them nicely if you manage to land a twave on them with rotom. one change that i think would be helpful is max special defense with careful on hippowdon; it takes away a mon specs latios can come in on, as draco meteor can never ohko which lets you slack off the damage and force it out. the special defense is also massively useful in all sorts of situations, give it a shot. if you do this, use a 25 defense IV so lead genesect gets an attack boost; without the +1 spatk, it won't even be able to 2hko with ice beam.
cool team gl