TBF, Gyro Ball is also pretty bad on most users. Even something with base 60 Speed (such as Aegislash) as well as 0 IVs and a negative nature, your target needs at least 110 base Speed fully invested just to be
equal to Iron Head.
0+ Atk Aegislash-Both Gyro Ball (79 BP) vs. 0 HP / 0 Def Gengar: 189-223 (72.4 - 85.4%)
For anything in the base 40 - 60 range, you're still whiffing against uninvested targets (i.e. most defensive Pokemon). Dhelmise has base 40 Speed and it still can't get to 80 BP against uninvested Mew.
0+ Atk Steelworker Dhelmise Gyro Ball (78 BP) vs. 0 HP / 0 Def Mew: 117-138 (34.3 - 40.4%)
The required difference is still so big that you need to be
extremely slow for it to work well. Combined with the fact that it's only really good with STAB (or Steelworker), there's only a handful of Pokemon that can actually use it.
Of the above, it's only Bronzong, Ferrothorn, Forretress, Stakataka, Wormadam-Trash, and sometimes Steelix that use it. Melmetal would also use it if it didn't have Double Iron Bash. There's a Smogdex set with Gyro Ball Aegislash, but it has to hold an Iron Ball to make it effective.
6 viable users is still more than what Electro Ball has at the end of the day, but it's a pretty low number for a move with decent distribution. I guess it makes sense that it's easier to make a Pokemon that's several times slower than average than to make a Pokemon that's several times faster than average, given that almost always want higher Speed.
Actually, I'm wondering if it's supposed to be used alongside pre-nerf Paralysis. If your base Speed is equal to or greater than that of a paralyzed target's base Speed, you're guaranteed to get max power due to the 1/4 multiplier. Which is "usable strategy for in-game" territory rather than "almost entirely pointless".