Take it when your collection has a real Terminator, Obliterator and Mutilator core and you want to play a positional game: threaten two places at once, refuse the fight you would lose, and land on the objective your opponent just cleared.
Be clear-eyed about the limits. It is three keywords, and if you own one Terminator squad the rule is a once-a-turn trick rather than a plan. Removing units also means not shooting with them in the turn they are in Reserves, so a Warpstrike list gives up a meaningful amount of output for its flexibility. And the two mitigation stratagems explicitly cannot stack on the same unit in the same phase, which is easy to forget under pressure.
One pairing note: this detachment is at odds with Devotees of Destruction on the same Obliterators. Rain of Ruin's Heavy rewards standing still; Warp Portals rewards leaving. Pick one plan for that unit.
Sample gameplan: deploy Terminators and Obliterators forward with a character carrying Akshur's Binding Runes. Shoot, then at the end of your opponent's turn pull the units that are exposed into Reserves. Bring them back with Siegebreaker Strike for Ignores Cover and Portal of Spite for the charge. Use Warp-tainted to lock a marker before you leave it, and hold Empyric Dislocation or Armour of Corruption, not both, for the unit that gets focused.