Edit: actually, this is a dual Xeon machine so its TDP is slightly higher than EPYC's.

That's not enough to explain. I highly doubt replacing the 12-core Broadwell Xeon CPUs with a current-generation 12-core Xeon (which would be Skylake) would catch up with the 30-40% performance lead that EPYC displays in their workload.

The Zen microarchitecture of the EPYC is quite impressive and it could just very well be a workload that Zen is particularly good at.

For example the fact EPYC can pack so many cores on a single socket means all the RAM and all its 64MB of last-level cache are "local" to every core (at worst accesses go through the Infinity Fabric.) By comparison, in Intel's case when one of the Xeon cores need to access RAM or cache on the other socket, accesses have to go through the QPI link between the 2 sockets, and it has higher latencies and worse throughput than AMD EPYC's Infinity Fabric.

Comparing TDPs between manufacturers is invalid.

Why? It's all Watts

Lets just ignore the price point for now because the memory capacity are different.

But the performance, 24 Core AMD EPYC Zen is ~35% faster than 24 Core Intel Broadwell Xeon under the same frequency? Broadwell isn't even that old because Intel has only launched Skylake Xeon E5 not long ago. And the different between Skylake and Broadwell IPC aren't that much either. the max turbo speed are similar, and the Intel platform had the advantage of two CPU using two heatsink, higher TDP, higher heat dissipation more time for turbo.

And most testing has shown Zen to be about Sandybridge IPC performance. Something seems wrong here ( Or may be too good to be true )

That's just a hunch though.