I, for one, think Absorb is a great mechanic that should be brought back at some point. It essentially gives creatures some extra points of toughness each time something resolves, which is pretty cool. As for this card, I think it's pretty balanced. 5 mana for effectively a 3/4 that gives every other Sliver better +0/+1 is kind of powerful in the sense that it makes your Slivers that much harder to remove. That being said, a five-drop in a Sliver deck should just win you the game outright, like Thorncaster Sliver, Sliver Overlord, or Sliver Legion. Still, this isn't a bad addition to a Sliver EDH.
Pros: Gives Absorb to Slivers
Cons: 5-drop that doesn't win the game