1) If you still want to run specially defensive Drapion, I would suggest a set of Crunch / Poison Jab / Rest / Sleep Talk. With this you can beat a lot of the special threats and have some semi-reliable recovery. Crunch hits Psychic-types such as Sigilyph and Uxie and Poison Jab hits Grass-types such as Sceptile and Lilligant. It can also absorb sleep from the likes of Smeargle, Lilligant, and Tangrowth. If you don't like RestTalk, you can certainly run Taunt, and for the last move you can run Whirlwind (even though you said you didn't need it). Toxic Spikes is really bad in RU, so it's usually a waste of a moveslot as there are many common Poison-types to absorb them; it's a waste of a moveslot imo.
2) If you want it to be as fast as possible, you should run a +Spe (usually Jolly) nature with 252 Speed EVs in order to tie with other base 95 Speed Pokemon and outspeed everything below such as Rotom, Moltres, etc. I would recommend a full offensive set, but for a tank set I would try a spread of 248 HP / 8 Atk / 252 Spe with Swords Dance so you can hit harder while retaining some bulk.
3) a) I don't think there are any good Pokemon that can use Taunt + Encore + Hazards.
b) Whimsicott is definitely the best Pokemon to use Taunt + Encore on, as it has the Prankster ability; however, I wouldn't really consider Whimsicott to be good, but if you decide to use it, don't use the SubSeed set! Other Pokemon which can use the move combo are Primeape and Gallade... but they have better sets.
c) Good Pokemon with Taunt (besides Drapion) include Aerodactyl and Archeops. Nidoqueen and Magmortar can also use Taunt, but like the other Taunt users, they are too slow to use it. The former two also have Stealth Rock so yeah. Other Pokemon that can use Taunt include Qwilfish and Mandibuzz, but they should be used defensively.
Hope I helped!
EDIT: ninja'd -_-
2) If you want it to be as fast as possible, you should run a +Spe (usually Jolly) nature with 252 Speed EVs in order to tie with other base 95 Speed Pokemon and outspeed everything below such as Rotom, Moltres, etc. I would recommend a full offensive set, but for a tank set I would try a spread of 248 HP / 8 Atk / 252 Spe with Swords Dance so you can hit harder while retaining some bulk.
3) a) I don't think there are any good Pokemon that can use Taunt + Encore + Hazards.
b) Whimsicott is definitely the best Pokemon to use Taunt + Encore on, as it has the Prankster ability; however, I wouldn't really consider Whimsicott to be good, but if you decide to use it, don't use the SubSeed set! Other Pokemon which can use the move combo are Primeape and Gallade... but they have better sets.
c) Good Pokemon with Taunt (besides Drapion) include Aerodactyl and Archeops. Nidoqueen and Magmortar can also use Taunt, but like the other Taunt users, they are too slow to use it. The former two also have Stealth Rock so yeah. Other Pokemon that can use Taunt include Qwilfish and Mandibuzz, but they should be used defensively.
Hope I helped!
EDIT: ninja'd -_-