The team overall was not good offensively in game 1, and that was with Kyrie for most of it. We need JR now more than ever (which is why I imagine he was out there in OT, the offense was sputtering leading into it). He's a lot more important to this series than Shumpert (who is still very important in his own right). Shumpert at the moment is probably an average stand still three point shooter and doesn't space the floor as much as Smith, as he's obviously not as big a threat from the outside.
A lineup with Delly/Shumpert/Tristan/Mozgov gives LeBron absolutely no room to operate. Yes, the lineup is better defensively, and you need defense out there against the Warriors, but you need at least a little offense out there or you have no shot.. I imagine Delly/Shump/JR will get some minutes together anyway, and a JR/Shump combo without Delly will get a lot of burn too, so it's moot now.