Hi there bro, really cool team, i like much the core Deoxys-D+ Gengar, the only problem could be Starmie for them, but the choice to use Weavile makes all more interesting, anyway you have a bit problem with some pokemon, and i hope that i ll help you with my possible changes.
The first thing i can see, is the weakness to Scizor, especially the Choice Band set, you have nothing to opposite to his two Stab moves, Bullet Punch and U-Turn on an eventual switch in of Kingdra or Garchomp. An answer to him could be Gengar with Hp fire, like you told, but with the Stealth Rock in your field is really Hard to stop, you can only try to revenge, but is so predictable the possibilty of Fire move on Garchomp and an eventual offensive fast set can outspeed Breloom too. Other Bug problem could be Volcarona, as told you Mr.Green, has totally free setupp on Deoxys-D and you have nothing that can revenge or stop it, another pokemon that completely destory you is a Random Dragon with the support of the Choice Scarf, for example the Lat twins, difficult to trap for Weavile, and so on.
Well, the necessity of a steel that could counterattack, yeah not counter the dragons because you re playing an HO, and that can thake pretty good the damage of a standard Scizor (for superpower you have Gengar if is choice) is felt, so my suggestion is to replace
Lucario instead of Breloom, the work is similar, Boost and sweep the opponent, it s true that Breloom sometimes allows you to play 6vs5 but Lucario thanks to his access to double Priority and one that hit a large part of metagame with the possibility to setupp on an eventual loked Dragon/Rock/Ice move and with the help of Entry Hazard is devasting and help you against the above threats.
My idea is to use a moveset of
Bullet Punch/Extreme Speed/Close Combat/Sword Dance, in thisway you have the possibility to close the game much times, even if the oppo has behind pokemon like Gengar or Terrakion, the Evs spread is the obvious Max attaker with Life Orb and Adamant Nature.
I ve something about your Deo-D, Skill Swap is an amazing thing, that many times is much useful but with that set boosters with more of 90 Spd base could be a problem since you re running an HO team you can t allow that the opponent Setupp, my advice is to use
Red Card over Mental Herb, it allows you to don t worry about Booster, in this way your Taunt is pretty useless, because you already have the way to don t give free setup, and Taunter faster than him can give you some problem to the strategy since you have not more Mental Herb, so you have to replace
Magic Coat over Taunt, in this way you have the way to not be taunted and have the possibility to "Reflect" eventual Layer of Entry Hazard and set as much as possible.
The team is really cool, hope i helped, gl with it.
Tl;dr
...
(Deoxys-D) @ Red Card
Trait: Pressure
EVs: 252 HP / 4 SDef / 252 Spd
Timid Nature (+Spd, -Atk)
- Magic Coat
- Skill Swap
- Stealth Rock
- Spikes
(Lucario) (M) @ Life Orb
Trait: Inner Focus
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Swords Dance
- ExtremeSpeed
- Close Combat
- Bullet Punch