I think Tantalus is slightly overcosted at the moment, yet it is a very versatile centrepiece unit. It is tough, fast, has got excellent shooting and good CC and
can transport a few units... It can certainly play an important role in a well-rounded army list.
Haven't used my post-Codex yet, although I do plan to run it in a Cult of Red Grief detachment together with a dozen Reavers and a Blood Glaive Succubus on board. Turn 1, it moves 16", Advances further 16" and then makes a re-rollable charge... Yikes
Pretty sure it will draw attention away from my primary Black Heart detachment this way.