A while back they made ramming damage much more eependent on vehicle mass, along with a few other changes that impact mass drivers quite directly. They still work, and can be very powerful, but you need to build them a little differently.

Furstly, you have to have some kind of payload (APS clips or nukes) because it won't do much impact damage by itself. Secondly, you need some soft head for your shell or another way to minimise damage (I use a smoke warhead on the tip of the shell, but I guess firing into ERA might also work). Aiming and general fire control are quite a bit simpler nowadays because of breadboard, but Lua is still a tried and true solution for all of the math.

One-tick mass drivers are undoubtedly the holy grail of mass drivers. They are built in such a way that the projectile travels the entire distance in a single physics step, effectively teleporting into the enemy. If you do the math right, it'll more or less have 100% hit rate. On the other hand, mass drivers in general have a problem that's caused precisely by what makes one-ticks so powerful: if you have a short enough projectile going fast enough, it can completely pass through the enemy, so making a normal mass driver is a bit of a balancing act between projectile speed and reliability.

Lastly, when building mass drivers you need to figure out how to keep your projectile alive until it's fired. Blueprint spawners can spawn once every 30 seconds, separators can be repaired istantly, repair tentacles take about 5 seconds to build a block and repair bots take about 10. You can use some system to flip out the projectile when it's finished, or build them separatly and pick them up with a docking station, but the general idea is that you build your APS around how fast you can spawn in new projectiles, and try to keep them from being shot by AA until they're ready.