PoE and Diablo are now the Yin and the Yang of each other. One has perhaps an overwhelming amount of depth and the other is a casual ARPG you can "compete" in with rift boards. The people thinking D4 should be a clone of D2 must know that it's a retarded model for current games. Unless Blizzard plans to crank out content (Yeah fucking right) to keep people playing, it's a dead game one or two months in. If they just want to do box sale and then launch an expac every year maybe that's fine, but the D2 style of killing the same boss 1000000 times and never advancing your character past BiS uniques you just trade for, it won't work. Stealing SOME depth from PoE where your character matters outside of your same cookie cutter unique build could definitely give it more longevity, but if they want a figure-it-out-your-build style like PoE they'll alienate their fanbase entirely.
It in noway should be a complete copy of D2. Look at the remaster. Shit was dead in 3 weeks. It should definitely be more D2 influenced than PoE influenced, but PoE has had a huge player base for almost 10 years now so they're doing something right.