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No, you probably haven't seen battles with black dragons...
First, warlocks almost always have luck... and that's double damage + additional elemental damage (if they have that skill).
Second, all their stats go into attack, so they are many times stronger than titans (in terms of attack and HP).
Third, what are you going to use to kill them? They have complete immunity to magic, and only spirits can handle them in melee combat, and even then, only if they miss!
Why bother casting light spells on them? They can decide the outcome of a battle in one turn. I remember a battle: a dwarf against a warlock... I was just amazed when the dragons dealt almost a third of the damage to the warriors and all the priests with one hit, thanks to their luck!
Red dragons are a different story. The only downside is the lack of immunity, but their initiative and ability are simply devastating – and if you don't kill them, the next turn of the red dragons will cost you one stack!
But my choice is black dragons; I really like them (and they are considered one of the strongest level 7 creatures). BUT I'm not arguing that titans are very powerful; their ranged attack is second only to elves, but if there's an archmage or at least minotaurs, they become a formidable force... I know this firsthand!