If possible, I would really want mechanical accuracy to be under 2MOA.

That said, in an actual defensive shoot, shooting under 10MOA is usually more than adequate to get the job done. If you're shooting within rock-throwing distances, in the midst of an adrenaline dump, trying not to become perforated yourself, you're probably going to miss part of the time, so balancing speed and accuracy becomes more important.

A reliable gun with a shot-out barrel: if the rifle has a good zero, you're still looking at a solid hit out to 150m when the shooter sends the round on target.

Like any hobby, shooters will spend more money on hardware to wring out that tiny bit of gain because having to eat the humble pie to just go our and practice to make huge gains isn't as fun. This applies to me.