I am noticing w/ diamond aspis every step after the second in a skillchain adds an additional 1 second to the skillchain window starting at 2+ seconds to close step 3 and about 5 extra seconds to close step 6. effect only activates after closing first skillchain (step 2).
THIS SHIELD MAKES SOLO 6 STEP ON BST TRIVIAL.
QUite possibly the mechanic is close a step 2, get 2 extra seconds for step 3, close step 5, get extra 5 seconds to close step 6, etc.