I'm fairly confident Quake is quite good already, it's just very niche.
As a tank player I can see it being cost effective very easily. My Goliath got buried/stucked by enemy Nanos/Scalpels/Rogues/whatever? I'll just fire a Quake. If it saves my Goliath I just made huge cost by trading a 400m missile for a 2.2k unit and denying the enemy up to 880m of reclaim. Nearly 8x cost made.
Sure, cons could unstuck a Goliath or a Reaper as well, but I won't always have cons join my raids. They are much slower than Reapers or even Goliaths, get killed too deep in enemy territory, etc. And even if they are nearby, they still have limited buildpower. A Quake hit flattens the ground instantly on impact.
Even saving a single Reaper with a Quake is very cost effective, especially if one considers the potential reclaim value of the Reaper.
There are also lots of maps with cliffs. People usually assume these cliffs are impassable walls for non-spider units. Perhaps there's an elevated Stardust protecting the only non-spider entry to the main base. If I have Quake, I can enter your base through the cliffs with my Ravagers/Reapers/whatever and there's not much you can do about that. 400 metal for that is nothing in the later stages of the game.
Quake is essentially a 6000 range instant terraform bomb. Comparing this with the puny ranges of constructors and their limited buildpower it should become apparent how the Quake can be a valuable asset for supporting one's attacks and raids to enemy territory in the later stages of the game.
I'm not saying that a slight buff to Quake is not worth considering. However, a large buff would seem very unnecessary.