My best suggestion is changing how you attack.
Issue long attack orders with multi targets.
Punch a hole and push as deep as possible knowing your units might not make it to the end target.
Break into the back line split up and run.
My defensive suggestion.
Two layers of defense.
Expect a breach while you are away.
Plan around the fact that you might need to counter attack.
Position your industry well away from the front lines.
Add extra defense around those industries.
These things are by far more important in speed rounds for lightning wars can take place.
In ordinary rounds wars are slow.
In 4x wars can look decided and change direction extremely fast.
I have had many players push into my land take 10 provinces while I was sleeping.
I woke up counter attacked with vicious intent.
Pushed all the way to their capitals and sunk my fangs into their economy.
They did not.
Always target the enemy capital.
Morale drops much faster and thus having a by far more important impact in war then before.
Build central industry around your capital.
Build sky high forts with rail guns and arty.
Expect your last stand to be at the capital.
If they push that deep while you are asleep make sure you have a large force ready to respond.
They will take losses and morale hits as they push.
When they reach your high walls they will be at the limit of supply and that is when you hit back hard.
In a matter of hours the war would have changed sides.
Push them out of your land and strike deep into their land as they retreat.