So when A16 stable went live, I started a game with 7 friends and since we need a lot more space, storage, workstations, tools and weapons than a singleplayer or a duo needs, we decided than one (it was me) stays back in the base and keeps building it while keeping the workstations working and providing everyone with the newest and highest tools and weapons and assort the loot they bring back home. Back then I could keep up the leveling with defending against screamer and digging some sand and clay near the base. I was on par with the levels and thus could build all workstations right on time.
We will start a new game once A17 is stable and then again we'd like to have someone staying home and keep the base growing, running and safe. But with the new exp distribution he won't be able to keep up with the levels and thus he will be behind with workstations and crafting level. So the one person dedicated to build the base will be the last one to be able to build workstations. He will be the last one to be able to make concrete, steel, firearms and clothing. The tools and weapon he crafts will be of lower level than those of the others. Just because he won't be able to get enough exp near the base.
It's not like we can't adapt to that. We just won't have a dedicated basebuilder. Organisation will be a lot more chaotic, but we will manage it somehow. But what exactly is the point of talent trees, specializations and teaming up, if in the end everyone is doing the exact same thing? Everyone will hunt zombies. Everyone will loot POIs because of the zombies inside. Everyone will farm just as many stone (plus its additions), clay and wood as currently needed and everyone will craft his own weapons and tools. And if we don't plan ahead, six of us will have to watch the other two building at night, because it would be to chaotic for everyone building at the same time. Other than that there will be no division of labor happening despite having talent trees. Just because the exp gain distribution is way off.
So aside from the problems singleplayer and duos have, the one-sided exp distribution takes the whole multiplayer aspect and the talent trees ad absurdum. That mining gives materials in addition to exp may be an argument in a singleplayer environment and comparing two singleplayers to each other, but it completely fails in multiplayer games, since the whole team will benefit from those materials, while only the miner itself will suffer from less experience gained.
Also: If 7 players are out int he world hunting for zombies and one player stays back in the base, the probability of a wandering horde targetting him and thus providing him with exp is way lower than in a singleplayer game. With way less experience for mining and cutting trees, this leaves him to screamers as his only noteworthy exp source. And as we all now, screamer can spawn running zombies and dogs even on low gamestages. So it's not like there is no risk involved.