Here, they unbanned something that you weren't even using in SoD. Isra and Vidomina were rarely played due to their weak skill builds. And they already get 30% undead bonus at level 2, which is much more important than the "hypothetical" 10-20 levels sometime in the future. And after that, the Necropolis grows without the need to heavily level up these heroes.
The Enhancement building couldn't be built. Now it's a guaranteed 2% undead bonus. And previously, only sometimes did Necropolis computer opponents get a 5% bonus.
The same story with vampires. They simply weren't in players' armies.
Are you sure you played SoD with HotA rules?
In HotA, it's only used when Gosha and Tant are banned.
According to your calculation, Vidomina at level 20 has 36% with the current version. And in HotA, it's 30%.
Discord - Xocenk#2473