we did it before, and you can do it too so i don't see what is your issue
i'm sure giving a constructive criticism would be more helpful for the devs than called "miserable experience" wouldn't you agree?

Here a pic for you in case you think i'm lying http://imgur.com/TRrBmce
i just have done it again with some random ppl

I've beaten it too, or did you not read the very first sentence? And the only times have been with 5 players, never the 2-player versions.

It's beatable pretty easily by using certain heroes such as enigma, necro, phoenix, ursa, etc. Basically heroes that either build up a lot of damage or deal percent damage. I've beaten it solo several times, but almost always by using some such hero.
The bosses just have too much health and armor to be able to consistently beat with most heroes, and it makes the game mode a lot less fun when you know you are going to likely lose if you didn't pick something like phoenix or enigma.
Been trying out some different strategies, and have found out that the earth bear's stun can probably be disabled by break. This is just going off of the few times I used silver edge against him or played shadow demon and used aghs and didn't notice any bashes during those times, though it could have just been luck. Hex is pretty effective in making them unable to deal damage, but doesn't do a lot on the damage front.
Best advice I can give is to take out either the storm or fire bear first. Storm steals around 200 damage from you, and his lightning strikes tear through your armor, making you very weak. Illusions are a good idea to use against him because they will soak up some lightning strikes. However, if you do use illusions be careful for the fire bear, as he has the fire binds of ember spirits and will use them if there is more than one hero or illusion near him. This can really hurt you because you won't be able to blink or run away when they start attacking you. The earth bear has the least damaging skill set, but he buffs the other two and his bashes can be deadly if the other two are alive or he just gets lucky. Since he has so much freaking armor and magic resistance, best to just kite around him until the other spirits are dead. But if you must fight the spirits together, take advantage of cleave mechanics if you are a melee hero or kite around them if you are ranged. Cleave deals damage based on the primary target's armor, so have the lowest armor spirit be your primary target and then cleave the other two for a lot of bonus total damage. Almost no hero except for like abaddon can tank all three of the bears at once without dying quickly though, so keep that in mind. Also be aware that the lightning bear's storm ability hits structures as well, so if you are fighting near your base, expect to lose towers very quickly. In addition to that, always make sure that the bears are either far enough away from the ancient or are actively chasing you. All it takes is for one bear to not be targeting you for a few seconds for your ancient to be dead.
Keep a heart either on you, or in your stash, so you can retreat and heal. Keep a refresher in your stash, as it gives an extra life from your rapier and has a shorter cooldown than the rapier as well. Also great if your hero has a long cooldown ability, though saving it for the extra life is essential. Always have buyback available, an extra 10 points in a stat or a single item is not as important as an extra life. Blink boots are very useful here, as they will allow you to escape the bears when you are low health. Be aware that the bears are all constantly regenerating about a hundred or so health a second, so they will regain a lot of health whenever you run away, so only flee when you need to.
You can just straight up kill the brewmaster when he splits because those spirits have the spirit health of the regular brewmaster ultimate.
But most of all, you almost guarenteed to need a hero that can deal a large chunk of their health very quickly, otherwise the fights can take a very long time.

We've done it pretty convincingly as WK LC. (not cheating with alchy).