I've wandered alone between most story-missions, but I'll try to get a PUG for free roaming also. Solo play is a fun little popcorn shooter, but I expect it to wear out it's welcome quick. And yeah, the "elite" enemies that take a few clips to put down are annoying, especially if it's one of the short-ranged powerhouses or snipers. These guys pack a punch, which is normally balanced by their vulnerabily. But the elites are classic examples of what Yahtzee called regular enemies that ate more protein bars. Instead of being a sort-of exam on the game mechanics, these bastards break it by being able to waltz right through your fire and shotgun or flamethrower you in the face.
The enviroment you walk around in is very pretty and atmospheric, it really sells the mood of the game. Too bad the rest of the game storytelling methods aren't that good. There's very little integration of the game mechanics with the supposed setting. The intruiging concept of being a sleeper agent who's turned active when your hometown is in desperate crisis is kind of neglected. Honestly, nothing would've really changed if they'd said you were a Navy SEAL, except that you'd presumably have a smaller selection of outfits to choose from. (Not that it matters, since all the ones I unlocked are pretty dull.) And don't expect the desperate situation to lead to any gameplay effects or moral choices. If it has a red health bar, kill it for great justice and move on.
I kind of bought the game on a whim since I was done with XCOM 2 for a while, and I mildly regret the purchase. I've had fun with it and may have a little more, but I probably wouldn't have bought it if I'd seen the Gothic Armada beta was accesible already.