B2B Live TBC 2.4.3

Q. Buff/Debuff list?
A. Grilled Mudfish, Scroll of Agility V, Elixir of Major Agility, Imp MOTW, Imp GoA, Blessing of Kings, NE Racial (1% dodge), Scorpid Sting, Insect Swarm, 5% base miss for a boss. (https://www.warcraftmovies.com/movieview.php?id=75441 + https://www.warcraftmovies.com/movieview.php?id=73639)

Holy pally: Salvation on party, Blessing of Kings on you (extra 10% agility) Hunter: Ice trap, scorpid sting (5% enemy miss chance (5% avoidance)) and misdirect/FD Shaman: Grace of air (77 agility) Another rogue: Won't help with your avoidance, BUT, its another sap/blind AND they won't steal aggro from you (feint or vanish) Druid: Mark of the Wild (slight stat buff) and insect swarm (2% enemy miss chance) (https://wowwiki.fandom.com/wiki/Rogues_as_tanks?oldid=1599981)

If your DPS isn't high enough, use Curse of Recklessness offset by Improved Demoralising Shout, get a paladin to keep up Improved Judgement of the Crusader and have a warlock spec into Malediction. If your tanks are dying, use debuffs like Shadow Embrace, Insect Swarm, Scorpid Sting and Improved Thunderclap. There are obviously many other options here, and the ones you choose will depend on your raid makeup. (https://www.engadget.com/2008-04-19-ready-check-brutallus.html)

Zusammenfassung von Quellen. Man sieht in den Videos auf jeden Fall (wenn auch sehr verpixelt), dass beide Debuffs auf dem Mob oben sein können.
Zusätzlich sprechen alle Quellen immer von BEIDEN Debuffs, statt nur Skorpidstich zu nennen (welcher ja der stärkere ist)

Man findet auch in den undokumentierten Patchnotes zu 3.0.2:

Scorpid Sting: Melee hit reduction no longer stacks with Insect Swarm. (https://wow-pl.gamepedia.com/Patch_3.0.2_(undocumented_changes))

Spricht ebenfalls dafür, dass es davor mal gestackt haben muss