Flash, a team I'm toying with now has a core very similar to this.++
The above combo has been one of my personal favorites that was first suggested to me by Bad Ass (Leaderboarder) and Reachzero, and I have been greatly impressed by its success for the time I've used it.
A short explanation of how the combination works...
Gengar @ Leftovers
Trait: Levitate
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature (+Spe, -Atk)
- Shadow Ball
- Focus Blast
- Thunderbolt
- Substitute
Gengar is a great Pokémon to balance both Tyranitar and Magnezone's weakness to Ground and Fighting-type attacks. Gengar is a great rounded Pokémon which can easily plow through teams that lack a reliable Special walls. Blissey, serving as a good counter to Gengar, is easily annihilated by Tyranitar. Gengar also attracts Scizor like honey attracts bees, meaning Magnezone gets an extremely easy switch-in. Gengar also deals with Lucario.
Tyranitar @ Leftovers
Trait: Sand Stream
EVs: 252 HP / 252 Atk / 4 Spe
Adamant Nature (+Atk, -SpA)
- Stone Edge
- Crunch
- Earthquake
- Pursuit
Tyranitar's main purpose in this core is to eliminate the Blissey which prevent Gengar and Magnezone from being able to deal effective damage to the opposing team. Tyranitar also serves as a great go-to-guy for dealing with Special attacks such as Choice Scarf Heatran which threatens both Gengar and Magnezone. Tyranitar's Ground, Grass, and Fighting weaknesses are covered by Gengar.
Magnezone @ Leftovers / Expert Belt
Trait: Magnet Pull
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature (+Spe, -Atk)
- Thunderbolt
- Substitute
- Hidden Power Grass / Hidden Power Fire
- Flash Cannon / Magnet Rise
Magnezone works as a great way to eliminate Steel-types such as Scizor and Forretress, which Gengar and Tyranitar have problems with. There's not much else to add here, as the set is rather self-explanatory.
Summary:
This combination of Pokémon is mainly geared to deal with each other's weaknesses, seeing as each Pokémon attracts an opposing counter that you should be able to deal with. As outlined above, Gengar will attract Scizor with is dealt by Magnezone. Tyranitar will attract Lucario, which is dealt by Gengar. Magnezone will attract Heatran, which is dealt by Tyranitar. However, this combination of Pokémon is more geared towards supporting a team rather than functioning as a whole, since this combination of Pokémon has little in stopping Gyarados and Salamence if they get a boost in, so using a Salamence or Gyarados would be an excellent idea along with this offensive core.
I'm currently running cursetar, and my magnezone set is fairly different (much slower, although I'm thinking about increasing speed, and with hp: ice/magnet rise). Gengar is the same.
Added to this was a mence (for salazone/magnemence), with roost/eq/d-claw/dd. Natural synergy, and works as a further luke check (it was mandatory for me to have as many checks to luke as possible when I have cursetar). Dancing gliscor could work here as well (enjoys sandstorm, and lack of steels).
Mence is benefitted further due to the fact that scizor is also one of it's most common checks.
Perhaps I could consider your tar set to help remove blissey. My team has a few problems, so I feel the need to rebuild it, although the core has great synergy. I will likely try and rebuild it off the same base.
Luxor, my advice is expanding synergy much more then simply throwing combos together (and even more then attempting to get them to fit your specifications like you described). You can pick a central combination, and then work off of it, expanding it.
Such a start can also help guide one to a team with a central, unified, strategy.
-The problem with filling the remaining holes is that I need to fill them with pokemon that fit well, and can cover the weaknesses well. Of the pokemon I mentioned, if 'gar goes down, specially based all out attacking mix ape says gg, for example.
EDIT: I forgot to give credit. I was inspired/got the idea from you after reading that post some time ago.