Diablo 4 is the perfect opportunity to correct that. The upcoming game will be entrenched in the context that Heaven is still recovering from Diablo's siege, and without so much heavenly power to go around, Paladins and Crusaders are liable to be few and far between Diablo 2 Resurrected Items. Instead, physically powerful warriors might be inclined to dabble in dark powers to gain what they lost.
Dark as that may be, there's room for a morally scrupulous character in the gritty world of Diablo. As Lilith rises to power and a new age for demonkind looms overhead, this might be just the right time for Blizzard to introduce players to a Blackguard class.
When a party brings a Paladin on board, they expect someone who can strike the balance between powerful damage and durability. A Blackguard would probably do the same thing. A Blackguard would join the Diablo 4 class roster as a sort of foil to the traditional holy warrior—still similar in their might, but different in their motivations.
Rather than being motivated by piety and a holy sense of justice, a Blackguard would be motivated more similarly to the Demon Hunter, filled with hatred for evil forced besides whatever otherworldly being empowers them.
The effects they conjure in battle would likely look similar to the power of demons, conjuring shadow magic and hellfire to tear through fiends without mercy d2r items for sale. A Blackguard would probably differ from a Paladin by being much more DPS oriented than its traditionally crowd control heavy counterpart.