Though I have no proof of this, I suspect that many of the original Legends are card versions of the creators' RPG characters. Those that aren't follow along in that vein.
Weatherlight and the sets that follow it are building on a storyline. As it is, WoTC keeps dipping into the past. Jolrael and company were first mentioned in Mirage block, and here they are again in the latest set. I would not be surprised to see more dipping into the flavor text and card titles of the older sets in the future.
What if part of the Invasion storyline involved the better Legends, such as Boris Devilboon, Kaysa, or Solkan'r the Swamp King? A trip to Karakas, Hammerheim, or Urborg (first seen in Legends)? An encounter with the remnants of the Balduvians (the Kjeldorans' ancestors?)?
As for Shivan Gorge's ability, it just screams out Multiplayer card, plus it fits red's trademark -- mass damage. Karakas is about the best Legendary Land for a chaos game.
Purraj of Urborg falls along the same lines. In a typical 8 player game, more than half either splash or run black heavy decks, followed up by green, red, white, and blue (in that order). With all those black spells being tossed around, Purraj of Urborg starts to become quite fun (as does Solkan'r the Swamp King).
If I remember correctly, Tolaria has the mighty ability to remove banding from target creature. That is bad.
That's all for now.