I've been tracing which units received balance changes throughout ROH's and DLR's patches. A few interesting oddities came to light that way.

Obviously, Reign of Heroes had much fewer different abilities than DLR. Morale boosts were much more common. (Elephants +1, Elven Lords +2, Knights +1, Knight Lords +2)

It got two patches, with only a handful of changes to units. In 1.01, Elven Cavalry got a Movement Boost from 24 to 30, and Treants got a significant nerf, down to 5 from 7. This was partially rescinded in DLR 1.01 when there strength was raised to 6 again, and they got a minor movement boost.

Elven Cavalry was apparently lacking a niche, with only 1 hit point and Morale +1, which could be provided by plenty of tougher units too.

In 1.02, Air and Fire Elementals received a buff to their abilities, +2 to Morale and Chaos instead of the +1 they had originally.

DLR 1.0 introduced 30 new units and new abilities, but only a few original units received changes at that point.

Elephants had their fairly useless Morale +1 replaced by Trample +1 and got their hit points increased to 3 from 2. They already had a higher than average medal chance in ROH, so these buffs made them one of the best combat units in DLR.
Plague Carriers might have gotten a buff to Disease from +3 to +5, if the ROH manual is correct.
Skeletons had their fairly useless Fear +1 replaced by Warding +2.
Wargs used to have a minor Disease chance, which got replaced by Warding +4, and Wolfriders also got the new Warding ability (+3).

The really major balance changes happened with DLR patch 1.01. Its changelog is readily available, and I'll address it in my next post.