I wouldn't say that the dlc is a disappointment, or that the ottoman tree is bad, but playing as the ottomans definitely has some issues (including bugs/bad design).
My ottoman game has been a bit more succesfull than most, it seems. After looking stuff up in the game files, and a few tries, i found out how to form the ottomans. I was lucky enough to have UK go decolonization and communist. I was able to take the greek and bulgarian focuses, and then defeat greece with bulgarian help. I got the French provinces in Syria through the focuses. Took out Cyprus, Iraq, Palestine, Jordan, Egypt and Saoudi Arabia afterwards. Now, it's 1943 and I'm kind of stuck. The main problem: MANPOWER. I should have about a million available manpower now, according to the tooltip, but I'm at 500k. I'm pretty sure I dind't lose halve a million men in my wars, so did I loose hundreds of thousands of men, dealing with the kurds?
I'm probably gonna end my game here, since I don't want to declare on the Axis. I won't be able to defend the Balkans, Caucasus, Cyrenaica and Ethiopia Fronts with just 2 24-division armies.
The main problems/issues:
-The Kurds being a huge manpower/PP drain (it seems way out of balance when compared to the 'formable nations', which just give cores if you control an area)
-Can't take the decisions to get cores on Syria (decision says I don't have all the french lands in syria, even though I got all of them through the focus)
-The decision to core Egypt doesn't core Alexandria
-The saadabad nations didn't join my alliance, even though the focus says they get invited. Got no feedback at all about this, didn't get a message to say they declined, either.
-The Saadabad nation didn't become my puppets after finishing the focus, even thought the focus said they would.
-The turks can't get to 5 research slots at all, if i'm correct, and the fourth research slot for the ottomans is only available if you're in an alliance with AH or Germany. Not being able to get a fifth research slot isn't really a problem, but Turkey is the only nation in the game that can't get it.
My own mistakes:
-Probably could have increased Manpower law, during the war against Greece, but I dind't do that
-There might be a better way to deal with the Kurds...