The thing is you're comparing current decks which haven't been rebuilt in order to increase the odds.
For example you can substitute Owl with a Spellbreaker which would have a big impact as the 4 mana wins with all other midrange deck's early game. Many early class specific minions could be replaced by the new weapons and spells as well.
Also the joust doesn't happen over the whole deck but on a specific turn (most probably we're looking at situations around turn 5 and 6) - where, if you mulliganed for your early drops you'll gain a few % against a deck that has more low cost minions.
I'm not saying this is going to be amazing but if you reliably can make it work 80% vs. aggro and 70% of the time against midrange decks the Joust could be worth it.