Limited Use

Had humanity successfully come up with attack methods that specifically harmed expert mechs?

The answer to this question was likely yes. These special weapons were not unheard of, but they were actually very rare because they were too high-end. Their cost was so prohibitive and their material requirements were so absurd that only special mech units of the Big Two and several first-rate states ever employed them in battle.

There was just something about expert mechs and expert pilots that produced results that couldn't be fully replicated through standard methods. True resonance, while difficult to accomplish, possessed potent extraordinary properties that served as a powerful amplifier.

Countering it was very difficult. In general, employing overwhelming firepower was the easiest but also the stupidest method. Resonance shields were specifically geared to resist a lot of ordinary attacks.