I guess if all you wanted it to do was some DPS... I for one was sad to see I gained no defensive bonuses without staff. And where the other moves are not really worth the cast time and Ki cost in general melee combat, Cauldron is. But it does go back to AP costs for me.
Focus is indeed very nice, but most of the things you've listed could be obtained with a spend of 11 - 23 AP. While I do think at least 2-3 AP is a total waste getting to 31, again a better way to look at it is what you gain for a chunk of AP vs spending that elsewhere. A few notes on what you have:
- Elemental Words are indeed nice, but really only on bosses, and the spamming it takes to maintain the vuln stacking ruins any finisher control you may want to have. Electric for Storm's Harness and Fire to support the most common Warlocks. Haven't crunched numbers yet, but likely swapping to Duality, so will either swap to Acid for the other warlocks I can help or just drop one entirely... but I see the moves as for elemental Vuln and only need to cover what the party needs. Another advantage of including Ninja Spy in your spends is Ki Strikes. Unbalancing Strike gives yourself or the tank SA damage - I will go into detail on the importance of this on my reply to your Ninja Spy comments, but based on those it is obvious you either underestimate the DPS SA damage provides or don't realize how it applies. Knock On The Sky is -20% damage - it was a big deal in raids with hard hitting bosses, and is an even bigger deal with Reaper. Eagle Claw can stack to 15% fort bypass for the whole party (see SA comments) as well as -15 AC which actually doubles to -30 due to the way the formula works... so anyone that was not already hitting on everything but a 1 would see a 5-10% full hit chance helping the whole party again. Fists of Iron is a great DPS move, but I prefer party support and consider all 3 Ki Strikes important... and you can't do that going into your important Aasimar tree and 31/41.
- Mystic Training
only applies to Finishing Moves, not combat DCs. This is helpful to Dark Monks but basically useless on Light Monks making every AP into it a "waste".
- I also play a DC build that main stats Wisdom - I pushed 90s, and after my Racial TRs are complete and the power creep of items, I should be able to break 100. I take every point of WIS I can from the trees and min-maxing it takes a spread... but it is also a balance. Much of a tree's utility is more important making it pretty low on the list. Henshin has nothing better to reach 30 with for an unarmed so is a no-brainer, but Shintao I have to decide between the WIS or Conditioning + Ki Shout.
Note that I was NOT saying that Henshin was a useless tree... just that I think the AP can be better spread out for more gain than just into Henshin.
Using DEX saves you from the investment into STR at all. That freed up gear can be used for other useful abilities. It also seriously boosts Shuri damage by applying your DEX to damage as well as extra Shuri throws. There are times you have to range: destroying gems and pillars in certain raids, killing people on ledges that you can't reach, or whenever there are mechanics you need to avoid and you don't want to drop your DPS to 0. Avoiding the need to use STR, though, I consider a big enough deal.
You can get BOTH Agility and Embrace the Void by doing a smaller spend into Henshin.
There is no "playing sneak attacks" - Sneak Attack damage is flat out DPS that triggers as long as you qualify for it. That qualification does not come from attacking from stealth, but many other ways. You can read the Wiki for the full list:
http://ddowiki.com/page/Sneak_attack
As a Monk, you'll get SA damage whenever someone else has aggro, whenever you stun a mob (which is your whole shtick with Stunning Fist and Jade attacks + Dire Charge), and whenever you use Unbalancing Strike. It does not take being a Rogue or investing deep into the Ninja Spy for SA damage to be nice. You can get items that can give +24 SA damage and +11 SA damage. As SA damage is 150% Melee Power scaling, that 35 damage turns turns into 35 * 1.5 * 1.5 (saying you have 150 MP, which you can do better than) = 79 damage per hit. That applies to every strike, double strike, and off hand/off hand double strike. That is an amount that matters. Rogue past lives and SA die from Ninja Spy and any better MP values can easily see that number climb past 100. It is also why Scion of Ethereal is the "DPS" Legendary choice as it makes Hide apply to SA for another large damage chunk. It's discussed in this very thread. That said, SA damage is important. You should try to fit on items as it is some of the biggest DPS boost items you can get, and you want Unbalancing Strikes so you can be sure everyone is getting that damage when you can't just stun the target.
It is indeed all about evaluating the gains of investing AP into one area vs another. The Undead Favored Enemy not being needed is indeed one more reason to not invest into the tree. Not wanting to invest into Knife use is a reason to not invest heavily into the tree. Haste Boost is still very nice, that 5% doublestrike stacks, and Deflect Arrows can be a big deal on high level Reapers... but obviously if that does not outweigh other gains, it's not worth the investment. Though I still hold that the 3 AP spend for 25% neg absorption and 3 PRR/MRR is
cheap and worthwhile.
The points I was making was not to say you were "wrong" or that your build sucked, but rather that I believe there are ways it can be improved, and my walls of text are to explain my reasoning, not to try and argue or disprove you. However that does indeed not matter one iota what I say if you are happy with how your build plays. The game is about fun, and that is all it should ever be about. My own monk was created the instant the servers went live with the class release and has gone through many iterations (many LRs, TRs, feat swaps, etc that are in the triple digits). I've gone 41/31 and countless other AP spreads. I want to and try to help people with their own builds, but I know for a fact that what one build works amazingly for one person can be terrible for another. It's good that you found a way that works for you.