I respect Nargott's opinion and knowledge, but in my opinion, you've forgotten what the original was like.
In terms of dealing damage, yes, Furies are needed. In the final stages, they either strike once and die, or hold a key unit (which only requires 1 Fury) and then die. A +10 bonus with a castle, yes.
The worst unit of its tier.
Archers, Centaurs, even Harpoons – these are ranged units (the first two are excellent) with good bonuses. Gargoyles, Zombies – they act as anchors. Demons – either a suicide squad (but more effective than Furies) or a semi-anchor/semi-damage dealer (I usually keep them and Pits, often choosing OD; DemonSD on a deceased AG.ru – I already explained the reasons). Dancers – damage dealers, like Furies, but with almost double the bonus and are very durable.

Let's compare the Megera to its closest analogue – Blue Dancers (also the strongest unit of its tier).
1) Speed: 8/14 for Megera vs. 7/15 for Dancers, roughly equal.
2) HP: 105 for Megera (with 4 defense) vs. 108 for Dancers (with 6 defense), a 10% advantage for Dancers.
3) Damage: 27.5 vs. 45 (both have 5 attack), a 60% advantage for Dancers.
4) Abilities: "Direct Fire" with a range of 8+1 (no retaliation + return) vs. Agility (approximately +30-50% to survivability).

In your opinion, doesn't point 4 compensate for the disadvantage in point 3? If Furies are to be buffed, the maximum should be from 5 to 6, because going from 5 to 7 is just ridiculous, making them thicker than Dancers, with almost the same damage and great ranged abilities.

If we're talking about practical realities, the Necromancer has weak physical attack (30%/10%) and, most importantly, in confrontations against melee units, they lack the overpowered "Defense" skill (only a 2% chance). Only because of this last point do the units seem not as strong as they could be under the command of a Knight or Barbarian.

Added after 38 minutes
If you're interested in the details of comparisons in test battles on their respective tiers (without heroes), then:

Tier 2 (top 3 best):
1st place) Alt Dancers, 100% win rate.
2nd place) Archers, 83% win rate (lost to Alt Dancers and Elemental Gargoyles, drew with Obsidian Gargoyles).
3rd place) Megeras, 77% win rate (lost to Alt Dancers and Archers, drew with Furies, Elemental Gargoyles, and Greater Demons).

Tier 3 (top 3 worst):
14th place) Alt Minotaurs, 23% win rate (victory over Obsidian Golems, draws with Cerberuses, Fire Hounds, Minotaur Guards, Warriors, and Warmongers without Blood).
At the same level were Warriors and Warmongers (without Blood).
15th place) Minotaur Guards, 20% win rate (draws with Obsidian Golems, Cerberuses, Fire Hounds, Minotaur Overseers, Warriors, and Warmongers without Blood).
16th place) Obsidian Golems, 10% win rate (draws with Armored Knights, Minotaur Guards, and Warmongers without Blood). Which is not surprising, because in these battles without magic, their abilities are not used