Going to DLR Thursday and Friday this week. Do we need to FP/MP Fantasmic!? Or is waiting in line an option without waiting in line for a long time?
Yes, you should get a fastpass. Having a fastpass for it does not delay you getting fast passes for the rides, so there is no reason not to get it.
If you are not planning to be in DL in the morning (or if you have MaxPass, if you are not planning to be in either park until the afternoon), you should get a lunch or dinner Fantasmic! dining package. Sometimes fastpasses run out in the early afternoon. If there are two shows, they can still run out but you’re more likely to be able to find a spot at the second show, even without a FP.
Is the dining package significantly better for seating/wait than FP?
Yes - the spots are in a prime central area. Perhaps someone can confirm (I haven’t been in a while) but I believe the more expensive packages have actual seating rather than standing.
But especially if you don’t have children there are plenty of good spots for FP (or even standby for the second showing). Most important is to not be behind trees or other obstructions and to be at the front of your area - ideally behind a planter or bridge railing (such as above Pirates).