The interesting thing is that even on highly dense workloads, the benchmarks and real world tests are showing that these hybrid core architectures are doing surprisingly great things.

I have more reading to do on the AMD side, so if you have more info than I take this with a grain of salt, but at least on the Intel side of the camp, the performance of a fully saturated E core is only slightly worse than its P core buddy, with 2x E cores meeting or exceeding the work output of a single P core + its hyperthread.

Even if the only purpose for the E cores is to run OS and other background workloads while your big processing job is getting unfettered access to the P core array, I imagine you'd see pretty great gains here.