Daemonhost is fine as it is. It’s a tough fight, but it is absolutely possible to kill it without losing anyone, or even having anyone go down. It’s another test of your group, asking the question do you have a tank? If you can’t deal with it, you should be trying other tactics, you should be looking at your gear loadout and asking yourself what role you fill in your group. Admittedly PUGs will have more issues, but that’s natural. It’s difficult to balance for PUGs and premade groups.
Your argument that it is ‘boring’ is rather vacuous. I could say the plague ogryn is boring because it just charges into you and slams people about while you beat on it, I could say the beast of nurgle is boring because it just goes around eating people and spitting slime everywhere. Neither of these statements actually really describes these fights, just like yours. Your is an attempt to dismiss the fight without giving an actual good reason for it.
In your opinion the daemonhost is unfun, and unfair. In my opinion it is a fun challenge the adds something different to the game. You can either bypass it, or if it is in a position where you have to fight it, then you should kill all the enemies around it before waking it, then pull it back towards where you came from and pretty much be guaranteed that that is all you will be fighting. Make sure your tankiest character wakes it up, and then pour everything into it (it isn’t that tough TBH), and if you can’t kill it before it downs then kills one of your team, then something is lacking in your team. think about what that might be and try to fix it for next time.
Unfair? It will only attack one character at a time, which you can determine by choosing who wakes it up, everyone else can just focus entirely on dealing damage with no worries that it will turn on them. This fight is way fairer than the other monstrosities which can force a fight anywhere, potentially with multiple specials alongside them.
I’m not saying it could not be improved, it probably could, but I can’t think how it could be done easily off the top of my head. Your suggestion will certainly not work. All that would do it trivialise it, and if that is your goal, just play on an easier difficulty. Some people like a bit of a challenge. Also, gear level appears to be more important in this game than V2, so play on a lower difficulty until you get to a level where you have the gear and feats to enable you to beat the tougher enemies. Also, the ridiculous hyperbole just makes it impossible to take you seriously.