Much respect for the effort DICE put into their soundwork. Would like to meet their sound team one day to shake their hands.
Getting on-topic now - To be honest a completely new sound engine should have been in development for Cliffs of Dover from the start of the project, if only to equally match the increased step in visual and simulated fidelity. At the moment we have a half-baked sound engine that is filled with some serious bugs which clearly can't be fixed and the sound engine itself is hardly more advanced than IL-2 1946 in terms of features.
Most sim games take the sound design of their games seriously as it is a big influence on immersion. They have custom-built sound engines designed for the particular simulation in order to try and replicate the overall sound environment as much as is feasibly possible. Watch some videos of Rise of Flight or DCS A-10C to see how realistic their sounds are.
Cliffs of Dover made a big mistake in not putting enough money / time into the sound engine and sound samples. The effect in percieved immersion is significant even if what is on screen is not 100% real. Not having actual sound samples of the iconic Merlin or DB601 at the very least (let alone using the same sound for both!) is a huge mistake. Not even trying to simulate the sound of wind hitting the cockpit and airframe or even differentiating the sound for when the canopy is open or closed can also be seen as lazy especially when such effects could've been used in all aircraft not only in this game but future titles as well
... and of course we have all the lovely bugs to put up with as well.