I may be a little late to this party, but I just finished my The Ultimate run with this build. While it had few tough moments, it was incredibly easy most of the time.
As some have mentioned, the Belt of the Royal Deadfire Cannoneer is absolutely insane for this build. I'd recommend it being the very first item you save money towards. It trivializes not only the Shades, but most of the early game. I ended up never taking it off, since it offers Flame Shield on nearly every fight and +8 worth of stats (+6 later with Ryona's Breastplate), without even mentioning Torrent of Flame.
I rushed WM 1 and 2 mainly in order to get Ryona's Breastplate, as it's such an incredible item for monks. Since I got Bittercut at an early level, I incorporated it into the build, resulting in my only two changes: I added Spirit of Decay and Two Weapon Style instead of Cautious Attack and the optional last talent. Using the Belt and Bittercut AOE abilities after Combusting Wounds proved to be a room clearer.
While Blood Testament is in theory great, it's still bugged to this day and must often be re-equipped. Since I couldn't be bothered most of the time, I ended up almost always using Ryona's Vambraces. Together with Hiro's Mantle they make for a great DR combo, besides the other benefits they offer. I would also often use Gathbin Family Signet to start some tough fights with Lord's Authority and for the AOE buff.
All bounties, Concelhaut, Adra and Sky Dragons and Thaos were trivial. I expected the Magran's Faithful to be tough since they gave my previous full party run a hard time, but I just bum-rushed and obliterated them. Alpine Dragon took a bit of practice since I was still underleveled and had obviously not maxed Ryona's. Llengrath also took some practice as I figured the best positioning. I used Drawn in Spring instead of Bittercut for that fight. Besides that, the only fights I vividly remember giving me trouble were some of the Battery Siren fights in Durgan's Battery and maybe some of the earlier tough fights such as Orimanth and Lilith, but all such fights can be made considerably easier with positioning and smart figurine usage.
On a side note, I had actually not finished the game before. I got bored at some point in Act 3 with a full party, and decided it would be fun to have my first completion also be my The Ultimate run, so I got a whole slew of achievements out of this. Thank you for the fantastic build, good Dr <3.
