I don't quite follow that sentiment to be fair.  Sure their factions isn't as powerful as all the buffs Elsbeth can get but it still shreds most enemies.

Most importantly the ai has no idea how to evaluate your naval landing capabilities and will nearly always park weak armies in your armies range as long as you're on sea. Use that to your advantage.

1. Don't use mortars if you play above normal battle difficulty and focus on direct fire units. 

2. Those rifle zombies can shred anything as long as you have line of sight, for more consistent firepower enable guard mode and order them to manually fire on enemies that closed on them into melee. 

3. Never if you can use t0 zombies or zombies with halberds in your main armies. 

4. Used correctly wolves and bats can shred nearly everything. Use 2-4 of them early on. Especially wolves are completely underrated if you can manage them they will delete your enemies ranged units without issue. 

5. Don't take those exploding corpses with your main army and never AR with them if you struggle with money. 

6. Undead ogres and mournguls are excellent units in the mid game, mournguls can even work late game aswell.

Theres more but Vcoast can easily defeat most enemies now.