That’s probably because they use advanced AI hosted on their servers. As for the user-run bots, let me present another old example, which I came across while looking for the previous one (with Trump vs a bot), this time it’s a video with one Kripparian trying to analyse their working:
https://www.youtube.com/watch?v=Kbf_zqXgGkk
I think I’ve still seen some instances of them glitching and timing-out like that recently, i.e. someone running an old bot or such.
That’d be one for you, I guess.
Do you really think or do you only think that you think? 
Well, official bots were offered initially (I think this practice might have been discontinued), and allegedly you’d be matched against them if you were waiting in queue for more than a minute, or so I’ve heard. These would labelled as ‘Your Opponent’, without any attempt to disguise them as actual players — and they were quite open about the feature.
Bots with impossible ratings dominating the leaderboards, though, is a different matter.
True, but as for the shame part, I would add: unless they openly declare it, like it used to be with Mercenaries — or nowadays with lower ranks.
So have I, but I believe I had the option to actually report it as a bot.
My personal theory is that they might use advanced AI to evaluate a player’s performance (just like a chess engine can compute ‘accuracy’), then adjust random effects and especially card draw to help more… intellectually challenged players, so that the game is more appealing for the masses, meaning that a 60-70-IQ person can win against a ‘pro’ player and feel happy about it — that way you can make it much more popular than something that would require brainwork and skill.
I can almost foresee this theory’s being attacked with various arguments, including those about psychological biases (well, not really… few on this forum are capable of handling such topics), but you’d have to explain me what’s the probability of not drawing at least one copy of four necessary cards after cycling through half or three-quarters of your deck… five times in a row every day you play, while those you report as bots — or just simple netdeckers — virtually always get a perfect opening hand, curve and top-decks, to convince me otherwise. That’s a slightly different matter, though, although related to AI employed by Blizzard.
I’ve pointed out many times that patch notes are notoriously… lacklustre, so they might not help you. I think the bots in question might have been discontinued, as said earlier, but it was a while ago and I don’t remember the details.
Not really. By the way, you forgot also the ‘ridiculous’ threads, which probably overshadow the ‘rigged’ ones in popularity.
Judging by these and some others, I get a feeling sometimes that I’m in a facility with giggling or raving… alternatively gifted and talented persons, with some exceptions, of course.
Can’t say about it definitively, but it’s possible, speaking of which…
If you look at something like Zephrys, it’s quite obvious how exactly such rigging is technically possible. To describe it without being too technical, ‘If you play too well, wish for a perfect card in your deck and put it to the bottom’ or ‘Wish for a perfect counter to your deck, then match you against it’, for example — wouldn’t be that impossible or even hard to implement.
Only in theory. A chess grandmaster or even master would probably tell you how hopeless and frustrating it feels playing against an engine, so they usually don’t.
You probably wouldn’t wanna be the average guy facing a boxing champion on the ring — that’s how ‘fun’ it would be for you, being beaten up like a punch bag without a chance do to anything.
I’ve been thinking whether this could be possible due to some connectivity issues or such, but in these cases you’d see ‘Your Opponent’ on the game screen, while their name and battletag would be visible on the side panel. I can’t readily think of an alternative explanation…
PS Sorry if I missed something important and noteworthy.
(Two posts merged, some updates and edits made)