For original Diablo, defeating endboss was barely hard, depending on character. With Rogue, just pushed levers to unlock walls where Diablo was in, aimed cursor at 90 degrees straight at boss, and just kept on shooting, kept him in stunlock and ended it without having to go through whatever minions were with him. (From a distance assumed)
And a thing did like about D2 in ver 1.00 was mass effect of stacking spells. Immolation Arrows worked like constant fire burning, until they came up with something called casting delays. Just as well, bosses and magic users in Act III Travincal were literally stacking up streams of meteors/blizzards against me.