First of all we've seen Harden play with an elite big man before, Dwight Howard, and it didn't work out well.
Also, Harden played with Chris Paul, Melo, and Westbrook on those Houston teams that you reference.
I get that it's only 2 games so far but Harden is +27, averaging 28 ppg, 14 assists, 9 boards, and is shooting 58%.
Embiid is +22, 36 ppg, and 9 boards.
They look like a really good fit together. Sixers are 2.5 games back from 1st in the EC. Ben Simmons is still out definitely.