There is hard, Nylon plastic shank right underneath the ball of your foot because of a design oversight. Merrel must change the shank design back to the Moab 2 to regain comfort in smaller men's and larger women's sizes.

This is not an issue with a single shoe: I've purchased three different pairs in three different sizes to see if any are more comfortable -- all of them have the same stabbing pain right under the ball of my foot.

The Moab 3 have a redesigned footbed, including a longer, lower quality shank which is the same in many different sizes of shoe. The shank is about half an inch longer, and has been moved forward by about a quarter of an inch.
The shank is so far forward now that it's right under the ball of my foot. The shank in the Moab 2 was shorter and thinner, providing stability to the shoe without impacting comfort near the ball of the foot.
The shank has gone down in quality too -- the shank is now thicker has two holes which are punched, front and back. The holes when punched leave a "dip" in the shank, causing there to be dead space in the footbed, and a feeling that you're stepping on a ledge right on the ball of your foot.
With this design, the shank is so long and so far forward that the shoe doesn't bend except right in the toe, causing the ball of the foot to be compressed against hard plastic when pushing off. It's difficult to wear these for longer than an hour without serious pain.

I had to modify my shoes to get them to feel "okay-ish." I cut out the front part of the shank in my Moab 3 (women's 9.5 wide), and replaced some of the missing space with foam from another shoe.

@Merrel, if possible I would like to very briefly (< 15 minutes) discuss the issue with someone to articulate exactly the issue that I'm having and to help improve your product. I loved my Moab 2's. I'm really sad to see and feel a decline in comfort in the 3's, and I'm worried I might have to hike the PCT on a different shoe.

-> Bottom line
It feels like there's a lump under the ball of your foot because there's only two small contact patches on the bottom front of the shoe. Either bring back the outsole of the Moab 2, or spread out the lug pattern to give the shoe even standing pressure so there's no a huge bump under my feet! I'm giving this version a 1 to catch the attention of folks -- it really feels like Merrel skipped some steps in the design review process.

Let me explain:
-> The softer outsole with lower contact surface area is the problem
From the Merrel Moab 2 to the Merrel Moab 3, the outsole has softened and thinned.
The 2 had a very stable platform with a lot of contact surface area at the forefoot, giving you a nice firm, stable surface under foot with a soft midsole to cushion the ride. The 3 has a softer/thinner outsole, and lots more dead space between lugs. On this rev, the two middle lug patterns on either side of the sole take the entire pressure of the boot in a roughly ~1" horizontal strip. This means you'll have lots of pressure on a small portion of the shoe at the forefoot. After a couple of hours of standing and walking, you'll start to feel a lump that gets real painful under the ball of your foot.

The contact patches on the Moab 3 are also more horizontal than forward. There's a significant amount of dead space behind the two lugs, and the sole and mid sole are soft enough that it makes it feel like you're standing on a ledge or a rock at all times.
The Moab 2 also had ground-contact material that stretched all the way from the central toe to the central arch. This gave plenty of support right behind the ball of the foot/at the central fore foot. With that material gone in this new revision, there's much less support of the arch and metatarsals.

-> Wear pattern is less supportive
The 3's contact pattern stays pretty consistent with wear. This is a bad thing, because the sole of the shoe never adapts to how you walk. The 2 got more and more stable as the shoe wore down.

-> Okay, so what should Merrel do differently?
In your next rev, either:
A) add more contact material back under-foot like the Moab 2, and reduce the spacing between lug features. Kill off the dead space which gives this boot a lumpy ride and add stiffening material to spread the pressure on the foot out.
or
B) make the sole of the shoe flatter on the forefoot. The Moab series of shoes has a very curved shape, which is natural, but this lug pattern with soft rubber is incompatible with this shape. The rest of the lugs need to be able to contact the ground to spread the pressure, too! Lots of shoes with softer outsoles have adopted a fully-flat design, but Merrel could certainly find a good balance of outsole-arch with forefoot flatness -- this is exactly what a worn pair of merrel Moab 2's natural pattern is like.

Finally, the shoe also got a little more narrow in the toebox, it feels like. My 2's never bothered my pinkie toes, but the Moab 3 just absolutely kills my 5th toe after a long day of walking.

Bottom line up front: To be as comfrotable as the moab 2, Merrel needs to move back to the Moab 2's insole (Kinetic Fit Advanced Footbed) and slightly soften the mid sole.

Pros of the Moab 3:
It's a good boot that's supportive and fits well. It's grippy and relatively light for a hiking boot.

Cons of the Moab 3:

-> The insole is much worse in the Moab 3 than in the Moab 2. The 2 had a pressed and perforated EVA insole that was very responsive and stayed springy for years of use. The 3 has a blue metatarsal pad which is inlayed into the insole. This portion of the insole is very, very unresponsive and lacks the same amount of cushion and responsiveness as the 2's forefoot insole. After a single day of use, the blue areas on the insole are flat and have no spring. The result is a fit that feels like i'm walking on a hard surface.

In my attached images, I've applied roughly the same pressure to the front of the insert to demonstrate how the Moab 3's insert is very flimsy at the forefoot. The older insole is much more sturdy and spongey in the same area. You can purchase the same kinetic fit insoles as the Moab 2's for extra, but only in whole sizes :(

-> The midsole is stiffer than the Moab 2, and this contributes to the pressure at the heel and the forefoot.

Both of these means the forefoot experiences a ton more pressure and feels much stiffer and less comfortable after walking out of the store. It's more uncomfortable to stand for hours or walk for miles, and it feels like I'm closer to injury at any given point than with the Moab 2.

I’m a trail runner and hiker, and I hoped these would be my everyday and hiking shoes. But while they are highly rated by many review sites, and probably a great fit for many people, I found them clunky. I bought them online (on sale) without trying them on, that was a mistake.

I got the 10 Wide, because normally I need wide. But these have a capacious toe box that has my feet swimming. Separately, they are really stiff and flat-bottomed. When you walk, they go clop-clop, no roll. That’s common in many stiff shoes, and it’s not a function I like.

And they’re really heavy. It’s been a while since I bought pure trail shoes, and I’ve gotten used to my lightweight running shoes.

Otherwise, the shoes are well constructed. They are sturdy. If you like the way they fit, and the way they feel when you walk, then my guess is they’ll be a great shoe for you.

But I gave up on these and found a different brand (in store) that suited my feet much, much better. It’s the last time I buy shoes without trying them on though.