Yesterday, after seeing this thread, I decided to try playing with a Warlock and companions... I started with the Warlock, and then I only hired heroes with starting combat skills. The main drawback of the Warlock-Warrior became apparent during a battle in the siege of an enemy castle, considering the 1-level unit and 1.5-level archer in the Warlock's army. The Furies, which the Warlock specialized in, became almost useless, as did all other melee units. I had to start developing war machines. A surprise attack also helped...
By the way, I chose purely strength-based Barbarians, half strength and half magic-based Demons, and a magic-specialized race, Mages, as my enemies. I took a beating from the Demons, considering the high speed and initiative of Cerberuses and Nightmares. And there's no need to even talk about the Mages.
I came to the conclusion that the Warlock-Warrior can effectively fight against Barbarians, Dwarves, Necromancers, and other Warlocks specializing in combat skills, which is quite rare. This is my opinion.

Added 3 minutes later

That's why I only develop Chaos for the Warlock.

I think summoning magic is also a good choice for the Warlock. And there are enough spells in the guild. Summoning elementals + fire warriors is a significant advantage. And the low initiative of fire elementals (8) can be compensated for with mass haste. To prevent the main troops from dying too early, Heavenly Shield will help. And the Phoenix that the Warlock gets is no worse than the one the Necromancer or Mage gets.
I agree that Warlocks are simply born for Chaos magic. But summoning shouldn't be ignored either!;)