Having had time to think about this a tad more, here's my thoughts on the new cards from the Sliver deck:
Rukarumel, Biologist- Interesting card. Has some decent synergy with tribal decks. May end up a budget alternative to Morophon for tribes without a true commander.
Titan of Littjara- Another interesting card. I like it but for a Sliver deck it's more expensive to cast than
Synapse Sliver which is easier to cast (U vs UU in the cost). Granted this is on attack whereas Synapse is on combat damage. The tradeoff decision may come down to how "pure" you want to keep your Sliver deck. May fit better in other tribal decks than it does a Sliver deck.
For the Ancestors- Good card. I like it, has potential to hit six cards in some tribal decks.
Descendant's Fury- Intriguing but it depends on getting through with the damage and if you don't have a creature you want to sacrifice it doesn't do anything. Probably best in a tribal deck that wants to create tokens that you could then sac to get an "actual" member of the tribe.
As for the Slivers:
Taunting Sliver- I want to like and I feel like it can be useful especially to protect yourself after a big turn. The problem is at 4 CMC it's competing in a slot that's awful tight in most Sliver decks (generally there's only 3-4 4 CMC slivers in a deck, usually
Bonescythe Sliver,
Shifting Sliver, and
Root Sliver) and I'm not sure this makes the cut over them.
Regal Sliver- I've been looking for a way to put the Monarch ability in my Sliver deck and this works but again, it's at that tight 4 CMC spot.
Hatchery Sliver- I like the Replicate ability and think it could be useful but there's not that many Slivers that you'll care about doubling up on the ability the duplicated Sliver gives. The biggest one that comes to mind that you would want to is
Sliver Overlord and without a way to disregard the legend rule (which
Sliver Gravemother gives), that doesn't work. There are others like Muscle Sliverthat would be worth copying or if you're just wanting to
flood the board it would be useful.
Lazetop Sliver- I love me some
Zombies and I love me some Slivers but I don't know how useful this one is.
Afflict 2 is going to still get damage through when they block your
Sliver Overlord pumped creatures and the Amass Sliver 2 ability is interesting. This one will have to be played to gauge I think.
Capricious Sliver- Nice ability but you have to make sure you have the mana to cast all the cards you're going to
exile if you swing out and don't win the game on the spot. Could actually hurt you if not used smartly.
Overall I like
Sliver Gravemother but the new Slivers in the deck I'm not sold on. Maybe test playing them will change my mind. I don't know, maybe I just had too big of an expectation for what the new slivers would be (I was thinking we would get like a sliver with
Toxic).