Something just being random doesn't make it an easter egg if its related to the game world and lore. If Warriv wasn't part of Diablo lore already then you'd have a point. Your qualifier for Easter egg status would apply to plent of other objects that don't serve a purpose but still can appear.
Also the journal entry gives you some lore and story on what happened to Warriv.
"I return to Khanduras after twenty years, the burden of countless failures and tragedies heaped upon my shoulders. Am I being punished for helping that stranger hunt the Dark Wanderer? I always thought Deckard Cain half a madman, but perhaps... he was right. Perhaps he can banish the shadow hanging over my life."
Thats not an easter egg its giving atmosphere to the game by letting you see some insight into historical events in the game and what happened to past major characters.
If it is to be called anything it is Fluff/Lore. Useless to the main story and mechanics of the game but provides you some info about the "world" of the game.
By the way the link to The Den of the Fallen is a dead link. The proper link is http://www.diablowik...n_of_the_Fallen, the news post has added a The to the link. And just case you are unaware your battle.net ID is missing the 4 digit numerical portion and won't help anyone adding you as a friend/whatever.