Tier 3-4

The improved BAB of the unchained monk allows them to actually hit with their attacks, and the d10 HD does a little bit to make them less squishy. Full-BAB flurry of blows is actually a decent approach to combat, and the ki powers give the unchained monk some versatility. And flying kick (which is basically the only choice for style strike) gives the monk desperately-needed mobility.

But the ki pool is still very tightly limited per day, with ki powers frequently burning several ki points at a clip. A lot of them are reactive, too, spending points and actions to undo dangerous effects you would really rather not have to begin with, and that most characters seek immunity to where possible, making those powers redundant at high levels.

So the unchained monk ends up being pretty good at one thing (combat), with a little ability outside that. But not really decent at everything, or really great at one thing and ok at the rest. When compared to 6th-level casters, the typical sort of tier-3 class, ki powers don’t really keep up. So you could argue that the unchained monk is towards the top of tier 4, or the bottom of tier 3.

More in-depth analysis

Since a point-by-point analysis was requested, here are more details:

Changes

• Full-BAB and unchained flurry of blows: This is a pretty big deal. The chained monk has very serious accuracy issues, which this directly addresses. Flurry of blows can actually live up to its name, instead of being a flurry of misses. The full BAB also helps the unchained monk qualify for feats, which is very helpful.

• d10 HD: On average, +1 hp/level, which isn’t great but it’s definitely an improvement, and a direly-needed one. The unchained monk is still very squishy, but this helps.

• Monk weapon proficiency: unarmed strikes are, if anything, even more important to the unchained monk than to the chained monk, so this isn’t amazing, but it is nice and there are some options in there that could be thought of more as a tool you could pull out than a proper weapon. The need for magic weapons later in the game makes this difficult to continue to use at higher levels.

• Ki powers: several of these are pretty good, qinggong power in particular. But Wis+½Level/day is a quite strict limit. Definitely good but not comparable to the 6th-level spellcasting that is the hallmark of a lot of tier-3 classes.

• Style strike: most of these are meh to garbage, but flying kick is excellent. Every unchained monk ever should always pick flying kick, period. Which is a terrible design, but at least a great option does exist here.

• Poor Will: why?! This was just so unnecessary. Anyway, while the unchained monk has plenty of reasons to pump Wisdom which mitigates this as an actual weakness, it only exacerbates one of the biggest monk issues.

Unchanged issues

• MAD: while full BAB and a d10 HD slightly limit how important Strength and Constitution are to an unchained monk, they are not nearly enough, in and of themselves, to obviate these ability scores. Moreover, Wisdom is even more important to an unchained monk than it is to a chained monk, due to the intense need for ki points and the poor Will save. That means that the unchained monk needs great Wisdom, good Strength and Constitution, and decent Dexterity. That is just more ability scores than Pathfinder supports. This remains a massive problem for monks, even once unchained.

• Random fluff features: they still exist, and they still don’t matter.

• Traps: the monk has always suffered from a wide variety of trap options presented, things that you can choose and that the books present as valid options, but are actually much worse than other options you could have chosen. The unchained monk is in fact worse in this regard than the chained monk, like the style strikes having one great choice and everything else being, for lack of a better word, wrong, and ki powers being of wildly varying effectiveness.