I still think non-Droppod melee Dread will have huge problem in getting into combat. Yes, by your calculation, your Dread will be at 2 inch away from enemy deployment zone at the start of 2nd turn assault phase. But it is always better to assume your opponent knows how to counter deploy / counter play an all out assault army, where he/she will have the unit deployed / moved as far away from you as possible. Considering the "thickness" of a deployment zone, his/her unit may still be around 12 inches from your footsloging Dread at the start of T2 assault phase, making your charge almost Impossible.
So I want insist my recommendation: the Death Company Dreadnoughts do need Droppod (or Stormraven if you playing fun game).
Hope that could help you. Good luck.