Here's a "professional" fact, not even opinion:
We don't know. Meta has changed in every other season mid-season, and the meta as we saw it one week before season start has almost never been exactly the same at the end of the season.
Currently, it looks like 4p is sup monk, sup barb, LoN WD, and necro as RG killer. In 3p you take any of those out (except for monk). In 2p it's even more uncertain, probably monk+WD and monk+wizard and monk+necro depending on what you want to fish for (RG with adds for WD or good mob type for an RG killer DPS). But honestly, all that is just super second guessing. We have no clue, especially since we might not even have seen all of the necro changes, and the current iteration is just out for one week. And I personally am 100% sure there's gonna be other exploits/bugs so I expect a rough season with lots of changes and potentially even a shortened season (like S2).
2 DPS necro is unlikely; you can certainly do that, but having two classes is almost always beneficial, and especially once you go above GR100 the monk is almost irreplaceable thanks to its powerful healing (alongside lots of other useful buffs). But it can work - there's a GR105 clear in 2p in Europe currently by a Hammerdin+wizard. But of course they're paragon 3000 and could potentially clear GR110 solo themselves, so that puts that GR105 in a different spotlight.