Dredgevine could be the Modern deck I enjoy playing most. If it does well, you can do crazy things, such as play a turn-2 Lotleth Troll, discarding one or more Vengevine to pump the Troll, discarding a Gravecrawler as well, and then casting the Gravecrawler from the graveyard to put the Vengevines into play with haste.
Unfortunately that does not always happen. Most of Dredgevine’s key components are weak by themselves. Lotleth Troll, Gravecrawler and Bloodghast seldom win you the match unless you can get them out before your opponent stabilizes. Even in a Modern format without too much graveyard hate, the deck struggles against other creature decks (especially those with Lingering Souls, Kitchen Finks and/or Voice of Resurgence). It also doesn’t do well against fast combo decks, where its game plan is to play one or two discard spells and then race them.
Nevertheless I am always looking for ways to improve Dredgevine, and this is another attempt. The new Origins card Evolutionary Leap allows Dredgevine players to sacrifice Bloodghast, Gravecrawler and Vengevine for value, and then return them to the battlefield. It also fixes one of the deck’s biggest issues; how to get Vengevine back from the graveyard when you have no creatures. Now you can just sacrifice a Bloodghast or Gravecrawler to search for a creature to cast.
I decided to go with a 4th color, White, because Lingering Souls gives the deck another angle of attack and more creatures to sacrifice to Evolutionary Leap. It makes the mana base a bit clunkier, but it may be worth the trade-off.