Heroes 5.5 WarGame Edition - Tactical Edition.

It depends on the goals, of course, but in general, I would argue... I'm telling you, an initiative of 6 is very low for a summoned creature, yes, 120 damage is great, but I'm afraid that by that time the battle will already be decided without the phoenix. With an initiative of 13, you have much more tactical options: to finish off someone, to take out the ranged units, etc.

120 damage with such an attack means it can take down 1 dragon. An initiative of 6 is quite significant, at least judging by how dangerous units with an initiative of 7 are (not in the original game, but in WGE).

The beauty of such a phoenix is that mages with low magic skills will fundamentally use it differently than mages with high magic skills. This creates, as it were, 4 roles:
1) a fast, weak unit with low magic skills (which is essentially what a regular phoenix is)
2) with a focus on peak aggression with magic skills up to 12
3) with a focus on peak strength with magic skills up to 17
4) with a focus on a passive tank with magic skills above 17 (a super-powerful replacement for the Wall of Swords by that time)

Well, this is already relevant. But isn't that too much of a limitation? Magic skills of 12... If this is the primary stat for a hero, which grows faster than others, it will be disappointing... Although the comment about elementals is also logical.

The primary stat grows to 12 by level 21, i.e., in a long game. Then there are bonuses from artifacts and leveling up. If the goal is to raise the stat to above 20 at any cost, then, of course, it can be done (with low other stats), but why play a phoenix then, when there are elementals that are focused on the highest stat?

There is, by the way, an option in the late game to get shamans or chieftains and tank with the phoenix. In this case, its low initiative won't matter. Shamans provide a 30% bonus (inspiration), chieftains provide a 10% bonus and 5 damage for each. Plus, there are several units in the game with an initiative aura of +2, as well as several units with a maximum morale aura of +5. And expert acceleration increases initiative by 2.2 times.

Finally, a powerful phoenix in a waiting position, with its speed of 6, keeps most of the battlefield in fear and is not afraid of being blocked by heavy units, as it deals a lot of damage with its fire shield.