Give BT Advanced 3062+ a go, stand off against a set of Demolishers, when you have Assault Mechs and WELL trained gunners.Vehicles are still somewhat vulnerable, as they have very few locations to scatter damage over, making it fairly easy to concentrate damage. And once their armor's breached, they have to be very lucky to survive another hit.
Generally on things like Shrecks or Demolishers, I'll precision shot on their flank armor, and take them out that way.
They CAN take upwards of three to four rounds of combat with consistent hits from multiple members of your lance with high damage weapons. I'm talking like I've seen these tanks last out multiple missile barrages, coupled with PPC, medium laser and large laser strikes from multiple members of my lance and just shrug it off like it is nothing. But... sometimes that fluke where you do JUST enough damage with an Autocannon causes a cascading ripple of crits, which is not as common as you might expect.