Savage coil 1 ideas :)

[Sove92]

The savage modes are built on the original versions, but I can see t2 enrage method being made impossible, if it was possible in original battle data.

In general, all bosses hit harder and have more HP.

Caduceus: Two slimes spawn at once. Damage buff stacks up slightly faster. A new mechanic, but I cannot think of any.
ADS: Chain Lightning leaves a debuff, don't stack too much. Double Rot at 33%, immunity timer is shortened at this point. But let's face it, removing the enrage method already makes this a savage fight for most of the playerbase.
Turn 3: The boss they removed! Jokes aside, T3 doesn't need a savage mode.
T4: Mobs have more HP and the waves are different.

T5: Infirmity from the beginning. Scourges hit harder and have more HP. Conflag is larger, forcing tank to move Twintania. Divebombs are unchanged. Snakes have slightly more HP, Asclepius hits significantly harder. Dreadknight moves slightly faster. Twister is back to its original mechanic. Twisters are used in last phase. Liquid Hell's voidzone ticks too hard for OT to camp under Twin.

Just my 2 cents, trying to see the fights in their original form.