I'm using many classes from AE in my Oathbound game. I generally prefer the way their spellcasting system works (along with the spell lists) to the PHB. Particularly important is the lack of divine casters, which make sense given the nature of the Forge and how I modified the cosmology for the campaign (sort of Oathbound meets His Dark Materials). From the PHB, the fighter (modified with d12 HD, 4 skill points/level, medium will save), rogue, ranger, barbarian, and bard (simple spellcasting) made the cut. Also, all skills are considered class skills for everyone. Its let anyone who desires to help out in social situations do so without dipping in a class just to get charisma based skills.
Warmains were ditched, as I've found them sub-par to even PHB fighters given their fewer feats, as were runethanes, due to being the NPC class equivalent of the magister. Witches were given a slightly toned down sorcerer spell progression and fixed spells known/readied, as I've found their minor powers in no way made up for the loss of high level spells compared to the magister.
Also changed were how exotic spells were learned. Exotic spells normally arent particularly "better" than other spells of their level, just more rare. To require a feat to learn one seemed on par with requiring a feat to be left handed, or have an unusual eye color. So we added a research system to help casters learn them without wasting a feat, and all spells from the spell treasury are considered "exotic".
Like you, I found the Diamond Throne setting pretty uninspired. Nothing reached out and grabbed me, and the world felt a little too stable for my tastes.
In play, its worked really well. Theres a magister, a greenbond/ranger, a ranger, an akashic, a righter/rogue and a mind witch. The players griped a bit about the healing (dealing subdual to the caster), but quickly saw how much MORE healing the greenbond could crank out compared to a cleric of the same level, and moved on. Also important to remember is that healing cures an equal amount of subdual damage and normal damage, so someone injured that casts a healing spell (and gets hit w subdual damage) and is in turn healed is cured of both with one cast. Its also allowed me to work in the return of Cure Light Wounds (renamed Ywannach's Touch) as a campaign event and player reward for completing a major series of quests to remove a blight from the land.