So Barbararians, Paladins, Rogues, and Rangers all get an "evasion" mechanic at 7th level. They improve a save to master, and treat a success as a critical success for that save. Nice. (Fighters don't get this exactly, but they go get Bravery at level 5 which is pretty good and have the best offense.)
Let's say this has a value of 2. 1 for the numerical proficiency bump, 1 for the evasion mechanic.
Monks get to improve one save of their choice to master at 7th level, but don't get an accompanying evasion mechanic. They only get +1 from the numeric bump. In order to get their evasion mechanic, they have to take the Monk's Evasion feat or wait until level 11. I think costing the class feat cancels out the value of the evasion mechanic compared to these other classes. I also don't really see why monk's get to choose any saving throw if they only have full support for reflexes for a bunch of levels.
Now, at level 11, the monk gains some value back. They get an evasion mechanic for whatever save they raised to master, and if they took Monk's Evasion (which would otherwise now be redundant) it scales into an improved Evasion mechanic for half damage on a failed save. Cool, it took four levels, but the monk now has a save value of 2. (Of course, other classes got new abilities at 11th instead of just playing catch up.)
Except... at 13th the Barbarian and Rogue get bumped to Legendary and get an Improved Evasion mechanic for free. This represent another 2 value, for a total of 4. The ranger gets this bump at 15. (Ranger and Rogue also get perception bumps at their respective points, which arguably bumps their value up again.)
The monk gets a chance to catch up again at 15th. They can bump a new save to master or a the same save to legendary. However, they get no Improved Evasion mechanic for getting a save to Legendary, only for taking a new save to master. That makes upgrading to Legendary a trap; you obviously should upgrade a new save to master to get another evasion. If you do this, you've hit your value of 4. This is your last save gain barring a 20th level feat.
Meanwhile, the Barbarian and the Rogue are getting another save to master + evasion package at 17th, taking their value up to 6. If you assign perception bumps a value of 1, the rogue is at 8 and the ranger is at 6.
Now, in defense of the monk, they do get an Ac bump at 13th and 17th. One could certainly make a case that an AC bump has a value of 1, which bring them up to a final value of 6 as well. I think that might be the logic, as Paladins and Fighters also get AC bumps but not save bumps past 7th. I can get behind this.
However, I don't think this excuses the monk falling behind between levels 7th and 11th. Expert unarmored proficiency + bracers only takes them to the same AC of equivalent light armor, minus a little touch AC. And this is compounded by bracers of armor lagging a level behind equivalent potency runes.
I also don't think it's save starting at expert is relevant to this comparison. The barbarian and rogue get 2 expert saves and expert perception. The ranger gets all expert saves and expert perception. Also, the feat cost to take a save or perception to expert is so low it might as well not exist by mid-levels.
And we also have some weird false choice feelings in there, to boot. "Choose your own save path" is a cool idea but not if some of those paths are traps or it makes you lag behind the other classes.) The easiest solution would be to have evasion mechanics kick in for free at 7th like every other martial, replace the 11th level ability with something else,* and give monks an Improved Evasion mechanic for any saves they take to Legendary. Bam.
*Three immediate options spring to mind. One is making the second path to perfection work exactly like the first and take a save to master + evasion. This would be the most consistent with the monk's legacy of excellent saves and higher level defenses.
But if that would make the monk's too powerful, you could simply move one of the 13th level features to 11th. It wouldn't represent a long term net gain, the monk would simply get it's bump to AC or unarmed proficiency a level earlier than some other classes. Arguably too tame, with the Barbarian getting Mighty Rage or the Paladin getting aura of justice.
Finally, you could add a new ability a la the aforementioned Mighty Rage example. Not sure what it should be, but you could probably draw inspiration from the class feats. I think Winding Path might make a good candidate to turn into a feature, as it helps the monk do that king of mobility thing.
I'm tempted to house rule this into my ongoing campaign, but I'd like to hear thoughts from others, especially any designers that may be reading.
"Monks are too powerful" is a problem I would like to encounter once in my life, just sayin'.
It feels like the reason behind delaying access to evasion and having the 2nd path to perception just give evasion is to keep people from having evasion for all 3 saves (though this is still possible with 2 class feats spent on the rogue or barbarian dedication).
But in general it feels like the high level monk is in a good place, but low level monks really aren't. I'm not sure if "monks are the delayed gratification class" is intentional or not. I strenuously dislike class feats like monk's evasion, since the "choose between the responsible defensive option or the fun option" is the sort of choice which is not fun.
"Monks are too powerful" is a problem I would like to encounter once in my life, just sayin'.
It feels like the reason behind delaying access to evasion and having the 2nd path to perception just give evasion is to keep people from having evasion for all 3 saves (though this is still possible with 2 class feats spent on the rogue or barbarian dedication).
That is possible the intention, but you could just not give a path to perfection at 11th in that case. They can get evasion/master to two saves just like the other classes, and at the same level. We don't need to split a class feature in half to accomplish that goal.
Can Paizo please just hire me as Monk Rights Consultant yet? Does nobody on the team there have their eye on this, because I REALLY don't want you to have to print a Pathfinder 2 Unchained'ed just to fix the Monk Chassis again.
The monk chassis is looking much better than the original core monk this time around. The action economy is a huge improvement for a mobile class, it can hit much harder with a dex focus than before, it has inherent accuracy increases, mighty fist items are cheaper... Really, I think evening out its level progression with other classes is the only remaining balance issue. (I'd like it if they got more class feats, but I feel that way about most classes.)
They may or may not be quite as strong as a well optimized unchained monk in the unchained action economy and some nice house rules condensing feat taxes. I had one of those before we converted to the playtest, and he seems pretty effective in both versions. That's also a lot of qualifiers though. A newbie with a PF1 monk, even unchained, will probably look way worse than with a PF2 monk.