In your opinion, which faction is the strongest in Heroes 5? Let's discuss the advantages and disadvantages of each faction.

They said here that "the Necropolis faction rules." But with minor artifacts, you can increase hit points not only for Gremlins but also for Gargoyles and Golems; after that, it's pointless. Next, we increase initiative and luck so that our units go twice while the enemy goes once, and so that the Banshee's scream doesn't affect us. Since the map is large, we have enough resources for all of this. Next, we remove the artifacts that give us bonuses to knowledge and put on bonuses to spell power and attack, ignoring defense. There's only one thing left: "KILL THE GOATS!!!" (c) ))))))))))))))
Conclusion: On large maps, mages rule; on the others, the Necropolis faction rules, and all others are afraid of them. It's not for nothing that in the main scenario, the Necropolis faction defeated the mages.

Well, you're quite the storyteller, removing some artifacts and putting on others, improving initiative, defense... large map, small map...
Everything is fair, but you're not playing against your imagination, but against opponents and neutrals who also develop and will periodically make raids, conquer mines, maybe even damage your army, develop themselves, and increase their army, especially the Necropolis faction. Regarding artifacts, you probably meant that they are sold in your shop, but the prices are so high that if you buy them all, I don't think you'll have a decent army by the decisive battle, and your hero won't be very well-developed. Minor artifacts also require resources, and as I heard in patch 4, they won't be able to be sold back, so you won't be able to experiment much with them. Minor artifacts are good, but your hero is a mage, and as I think, he is the strongest link in your army, so develop him.
P.S. "Kill the goats," I hope you meant something personal (a neighbor on the LAN, a brother, or a friend..., livestock in the pen...), and if not, then your statement is at least not politically correct and does not correspond to the noble name of a mage in Heroes 5.