Superspeed used to be an engi thing
Every class has seen its “unique” mechanics encroached upon as time has gone on. Engineer itself stole group stealth from thieves with stealth gyro.
It’s also a bit funny that two of your suggestions are dark and ethereal fields, which are necromancer and mesmer mechanics in the same way that superspeed is for engineer.
Because really there very few actual unique party level mechanics in the game. Most of them are like superspeed and ethereal fields and dark fields – they come in abundance on a specific class, and some other classes have very minor access to them. Access to superspeed outside of engineer is pretty rare, and no other class benefits from it as much by far. So superspeed still is an engi thing really, it’s just that some other classes can also use it on occasion.
im not special enough
please i want to be special
head here to discuss wvw without fear of infractions