So is this just a case of Bombardier building a bigger, heavier, faster version of the Dash-8, and forgetting to reprogram the A/P intercept logic for a more, shall we say, ...leisurely... turning capability?
I believe the avionics for the classics are delivered by Honeywell, whilst the Q400 is delivered by Thales. There should have been plenty of opportunities to create a good design from the start of the Q400.