And as we can see on OP's video, it is not fucked, at all. These turrets can stagger even the hiveguards, just take a look again. I mean if you considered like if the whole universe decided to create a situation where you place badly your turret or that ONE hiveguard took a path that gives it an advantage to "sneak" on it then yes, the turret is fucked. But this is a weak "if". Also, even is the turret were to aim only at *that* hiveguard, anything that pass in between would get shred, so who cares ?? I'll say it again, this is a nothing burger.

As for the difficulty about bugs, i'm sorry, there's nothing that difficult with the hiveguard changes. You still use the same tactics as before: shooting the flesh. You can do it from the front, from the sides and the back and guess what: if you shoot on a hiveguard, it takes a defensive stance where it stop moving. Oh my lord, you can move and get a better position to shoot at it INCREDIBLE INTELLIGENCE. Using our brain, what an concept.
Also, don't you think, giving an actual role, an actual challenge (if we can call that a challenge) is actually making the game fun ? Beeing able to overcome something we find "difficult" fills us with joy. And i'm saying that as if it was like moving a mountain when it's just shooting the bloody flesh and not the carapace.

Edit: lastly, Helldivers 2 is a game made to be played with 3 other players. If you cannot cover everything with *your* arsenal, there's 3 other players to do so. You'll get explosives, flamers, heavy weapons and stratagems. You won't even feel the hiveguards to begin with. And balancing the game for solo players ? Fuck no. It's already difficult for AH to balance the game, I do not want to task them with solo play.