Specifically the "Improved Stalwart Defense" and "Greater Stalwart Defense" (which the former turns into) are too lengthy.

A chain of 6 items seems a little excessive... mostly because those first three in "Improved Stalwart Defense" (ISD) are required if you want anything from "Greater Stalwart Defense" (GSD) ... to make matters worse, if you want anything in GSD tier 3'd you'll need to tier 3 all of the abilities in ISD which really really eats up a lot of AP...

My suggestion? Glad you asked. Not going to be easy to implement with so much going on in this tree, but: Change the progression of ISD so that after 2 ISD abilities you can progress to GSD if you like, or continue on to the 3rd ISD ability or both...

Similarly there is a lengthy chain for Reinforced Defense and Armor/Shield Expertise, it makes sense that they are linked, but makes it difficult to pick and choose what you'd like, I personally would be much happier if Reinforced Defense was not linked to Shield/Armor expertise, and possibly if Shield and Armor Expertise were independent as well.