prime79
Let's choose the three best heroes among the Dark Elves. There's one hero who is suitable for everyone – he's useful in any case – and there are specialized ones, needed for specific armies. They shouldn't be used for standard tactics (all types of troops and as much magic as possible), but that doesn't make them worse.
Sinithar is the best of all the heroes. Warlocks use magic in any case, so he will help everyone. And for those who specialize exclusively in chaos magic, he is simply a gift. This "gift" earns him the first place.
Irenna and Vaishan share second place. They enhance good units, and we can develop a special tactic that differs significantly from the standard one.
Irbet takes third place. Her ritual, which increases the mana reserve, can be very useful for many. The main thing is to develop a tactic in which the hero can actually spend a lot of mana in one battle. Perhaps it is worth creating a defensive army – with hydras. In any case, it is best for her to fight against heroes and very strong neutral units; otherwise, her specialization will not be well justified.