As the title said I came up with a potential 10-cost play featuring the new card Saronite Taskmaster. Before starting up, I want to clarify that this is NOT an OTK but only a fun combo that may lead to victory under the right circumstances.
In this way you will end up with a board full of decent minions (2/3s are not great but still better than nothing) and your opponent will be really limited in his plays, having only one space available to play minions.
Is this combo invincible? No
Is it counterable? Yes (especially if your opponent can buff their taunts in some way)
The idea of deadlocking your opponent's board isn't new, it was done in witchwood by Marin the Fox/Shudderwock combo. New expansion also brings us sweet Zentimo/Hex combo, which can basically consume 3 of your opponent's board spaces for 7 mana and 2 cards. Saronite Taskmaster could probably be a good addition to that meme combo, but other stuff you've mentioned is way too complicated IMO.
1) All it takes is a buff of some sort or a full board clear (eg. Hellfire) to completely dismantle all the effort you put into this. Hell, all a mage has to do is Frostbolt one of the guys and they can at least do something then. And now that something is behind a wall of Taunts.
2) Your ability to kill your opponent becomes extremely limited, because now you can only go face with spells or a couple of hero powers (your example of course used hunter). Preventing your opponent from doing stuff is kinda' meaningless when you likewise cannot do anything.
3) Whilst I hate the 'why use combo x when combo y is better' argument, I believe it is applicable when both combos use the same cards. In this case I'm talking about Cube shenanigans. If you're going to engage in Umbra + Cube hijinks, there are a million far superior ways in which to do it.
Now I'm not here to shit on fun. If you're excited by this idea and looking forward to trying it out then more power to you. But at least keep points 1 and 2 in mind because even you will struggle to enjoy yourself if those holes aren't plugged in some way. Even a for-funsies meme combo isn't that fun when it doesn't work.