These guys seem really cool.
Dune-Brood Nephilim: Since this guy costs four different colors of mana anyway, he goes along perfectly with the theme of fetching extra lands. I see him being played in a GBrw control deck (Train?) that can make him a powerful card without wasting too much energy on getting around blockers. It will be a solid card in a deck that can use a 3/3 body without worrying about the color requirement too much.
Glint-Eye Nephilim: The obvious use for this guy is to pump him after attacking, taking advantage of the fact that each mana expended damages the opponent and replaces a dead draw. Card advantage plus some significant damage is a recipe for winning, but is he worth it? My gut reaction is "yes." But I don't have any experience with a card quite like this one to make a comparison. The cards he reminds me of are broken ones that he can't hope to measure up to. I'm still unsure as to just how good this one will be. But he's probably even better than Dune-Brood. After all, there's no rule against pumping him up with something other than his ability and gaining much more card advantage than any Ophidian ever gave.
Ink-Treader Nephilim: This one seems the worst of the bunch (maybe). Copying spells is some cool stuff with other cards, but it seems unbreakable (and we want to break it, of course) on this guy. I can take advantage of the fact that my opponent has no creatures and hit this guy with something that pumps him up, or I can hit him with something to try and wipe all of my opponent's creatures (as well as my own) off the board. There are some spells you can use him with that will only help you and not your opponent. And there are untargetable creatures that can be used alongside him while you wipe out the opponent's creatures. But you can't do all of this at once, and he isn't good enough to have an entire deck built around him.
Witch-Maw Nephilim: I'm partial to this one, since I always liked Forgotten Ancient (which is similar). This guy is a rehashed Quirion Dryad (also similar) and weaker since he has a much more restrictive mana cost. The trample (basically) is nice, but the important difference is that he gains TWO counters for every spell you play. It's like Miracle Grow. Remember quickly Quirion Dryad became huge? This guy, once he's in play, gets huge TWICE as fast. It's silly to predict that he could be as good as Quirion Dryad (or even Forgotten Ancient, which is an underrated card). But it's close enough that I can definitely see it being used for the same purpose in casual games (and hopefully in tournament decks, although I am not so optimistic as to believe he's THAT good).
Yore-tiller Nephilim: All of these guys are decent. I don't know which ones, if any, will stand the test of time. But right now it really looks like this one is the best (and I mean really). Its ability is ridiculous. Dune-Brood and Glint-Eye have great abilities that are triggered whenever they successfully hit your opponent. Yore-Tiller doesn't have to. As long as you can keep it alive, it's there every turn to swing and bring one of your creatures back from the dead (attacking). That includes other nephilim and other Yore-Tillers in particular (although any of the others do nicely). And it's not like there have ever been cards that dump creatures into your graveyard. Oh wait...
In conclusion...
Yore-tiller = awesome
Witch-maw = awesome
Glint-eye = good
Dune-Brood = decent
Ink-Treader = meh
