Luck is a big factor in war, this game is set out to tell the stories of a war, sometimes, you can be the better general but things don't work out in your favour. You say Daemons are losing you games through no fault of your own, but its just as likely, statistically that their randomness will work in your favour, if you've played a lot of games and you're losing every time with daemons, the rules aren't the problem.
The rules are solid as long as you play the game in the spirit its intended, there aren't Seercouncil Death-Stars when you play in the spirit intended, no one I know and play with would ever dream of using that in a game, because thats not fun for your opponent, so people don't use it.
If you use a broken unit, you're admitting to breaking the game, if you use a RAW over RAI ruling of a rule, you're admitting that you're breaking the game.
I'm playing in a tournament next month where the rule pack specifically states that the even is supposed to be fun and tells you "don't be a dickhead", this is the kind of attitude wargames had for most of the 20 odd years I've played them, being a cheese-monger was a bad thing and if people used unbeatable deathstars or stuff like that, they were told to **** off.
Competitive people online don't seem to blink about taking these units that will ruin the game for the other person.
I don't know where these competitive people came from, but really, if they wanted a balanced and competitive game, they'd go else where, I can only imagine they like showing up with their broken army and stomping other people to get some validation and when the army they bought changes to be more in line with the fluff and they can't stomp people with it, they whine.