Awesome read, Umby! It really brought me back to the past.
I think I agree with the placement of these threats, nicely done.
Other mons that I believe deserves a mention is CB Slaking. It does a really great job at breaking through walls with its enormous attack. Pokemon like TTar and Metagross cant take hits from Slaking consistently. It also has decent bulk to check DDMence and other dangerous threats.
Flygon is pretty nifty, too, imo. Has some useful resistances and Speed and decent Attack. It can utilize its CB Set to put the hurt with STAB EQ, a Screech Set that can check Curselax and abuse Spikes, or a mixed Attacker with Fire Blast to dispatch Skarmories / Forretresses.
Although Gyarados has coverage issues, it does have 1 advantage over DDTar and DDMence - it can set up on bulky Water like Swampert or Milotic. It needs Magneton support, and must be wary of Aerodactyl, Zapdos, Salamence, and Gyarados with Thunder, however :/