Update on our efforts, We built an IK setup from scratch for our character entirely within the animation blueprint, we are using Anim notify events to tell our IK bone when to activate and de-activate. this lets us fine tune exactly when we want our feet to stop and start moving again with relative smoothness.
In addition, in the Details tab of the Two bone IK node, you need to set the end effector (your foot) to “World Space” that way it will use world location instead of component or bone space, which do not allow correct IK behavior.
Rough guide to what spaces to use for IK setups:
- Component: interacting with things inside your characters component tab.
- Bone: interacting with other bones in your character rig
- World: interacting with the environment
That’s not to say that IK wont work in these spaces, but you should probably use the right space for your IK setup.
(this is why the IK setup in the content example only works on things that move above the capsule floor, below that is out of range, it can’t actually move below that at least not normally.)
We use a layered blend per bone in the anim graph to blend the IK into the regular walking animations because, using the alpha on the IK bone node seems to not have a good outcome.
This lets us snap our limbs to the ground and have them stick correctly. however we are still having trouble when our parent bones pull the IK root too far causing feet to leave their desired location. I think we are close to solving that issue by using a bone transform node to move our hips closer to the foot furthest away.
If you would like more detail than that, give me a yell and Ill see if I can send pics of the blueprints.
(warning requires quite a few variables and we built some functions to clean up our blueprints because they got quite messy 
)
(note Im a beginner at UE4 but that’s roughly what I figure is going on. could be wrong, could be right.)