Speed is fine, there are much more broken things that need to be nerfed. SKs, looking at you...
Besides, nobody uses speed in pvp anyway (except some fighters maybe), so it doesn't affect you.
What other players do with npcs is not my concern, live and let live lol.
Wanna take down a boss without speed? You're free to do so, nobody is stopping you.
Speed actually makes it possible for solo players to beat some dungeons, when they don't have a guild/party. A big plus in my book.
Just my 2 cents
While you are at it lets also ask to nerf needle / bold strike from the game cause they 1 shot players
Needles don't one shot anyone except humans maybe, and that's if they aren't geared properly. Fighter has about 1% chance of winning against a good SK, and I'm being generous here xD. At least during current cap.