You clearly have no argument so you come back with the same moronic rubbish about being ‘a fanboy‘. So let me break it down for you:
Running ‘simulations’ or testing every possible combination of every card would take a very long time. A lot longer than what they can allocate for to have expansions come out every three months.
The team tests the cards (they play them) and know from previous experience (along with the data they have) what to generally avoid. But it is ‘nearly impossible’ to test what a combination of about 810 cards (the last two years of Standard) with their stats would look like. And since Hearthstone cannot use fractions (a card cannot have 2.5 attack or health for eg.), like other games to balance, they have to go with the most ‘educated guess’ they have on how to balance it.
So then the cards of a certain expansion come out, and some ‘creative genius’ in the community (after a few weeks of testing) decides to combine certain cards (old and new) to make a deck. Since he/she wants the most effective deck to win, he/she would use every tool available to do so, and the results are things like ‘N’Zoth Voidlord Warlock’ (back when N’Zoth was still in Standard), where the power level hits the roof.
It is something the team could have not ‘simulated for’, so then they have to weigh their options based on gathering information, watching matches,…etc to know where to effectively nerf, but still make the cards feel powerful (in case of legendaries for eg.) and also relevant (as I mentioned in previous post about how 1 attack or 1 health less can make a big difference).
That. takes. time.
Get it? If you didn’t, I suggest you go play Solitaire. It’s a better card game for you.