Yeah, you pretty much need Extra Wildshape and/or Elemental Shape to benefit from using all 4. You also only get them for 10 minutes at most. Not a big deal, of course, when a Druid (or really anyone) at level 16 is doing most of their dungeons in a single rest period (depending on party).
The resistances thing is a bug that's getting looked at according to MAB on Discord.