Super Speed doesn't work as it should.
If Super Speed isn’t increasing run speed by 100% as the tooltip indicates then this should really go in the bug reporting forum.
It absolutely works how it is supposed to, just like Fleet Shadow for thieves works as intended.
You have base speed of 100% out of combat (ooc) and 66% in combat (ic). Speed ooc and ic is capped at 133%, thus you max out movement speed just by applying swiftness ooc and neither Fleet Shadow or Superspeed are faster. But ic you have a base speed of 66%. Swiftness then puts you at 88%, slightly slower than a person ooc without swiftness. Fleet Shadow brings you to 99% and Superspeed maxes speed at 132% even ic. Nothing bugged there!
Have this for an overview:
Superspeed +100% /// ooc 133% /// ic 132%
Fleet Shadow +50% /// ooc 133รท /// ic 99%
Swiftness +33% /// ooc 133% /// ic 88%
Signet +25% /// ooc 125% /// ic 82,5%
Base ooc 100% /// ic 66%
Cripple -50% /// ooc 50% /// ic 33%
Chill -66% /// ooc 33% /// ic 22%