Did you ever play anything beside XI and XIV? When I mean play it's at a high level (so raiding etc.) If yes then you would understand how XI is slow paced, and there is no need to use recent content as Provenance Watcher to try to justify than XI is a fast paced game.
Overall, it is slow compared to most MMOs in the market.
Could it be WoW, Aion, Rift, SWTOR or even older games like DAoC,... These are fast paced games, where lot of abilities have typically have a 1.50sec or less casting time. Lot of instants abilities (but coupled with a GCD that's 1~1.5sec, still). Lot of mechanisms involving very fast movement from players in order to survive, etc. Cooldowns are typically very short. Encounters are short but very intense.
XI had nothing of this and still don't as of today (even if yes it did become slightly faster). You don't make your point valid by being an XI or XIV player only. You do if you played both of these games alongside other triple A titles in the past decade. That would allow you to say if a game is slow or fast paced. Being slow or fast is relative to others products in the market.