If Joust isn't good enough to build around, I don't think it's good enough to play at all, based on the cards we've seen so far.
How do you imagine a deck to be build around Joust to look like?
Like, "I'm running Power of the Wild/Feral Wolves/Demonfire instead of a cheap creature, because this is a joust deck"
That sounds terrible. I think they will enter in control decks that aren't focused on the jousting, but the jousting is good because they run big minions. Maybe new giant decks? Control pally, control shaman. They may end up being tier 2 kind of decks.
Polymorph was a very viable Magic deck, it ran 59 noncreatures cards and 1 creature card. It's hard to play 29 spells and 1 minion right now, but each new set will make it more possible to do that because we'll get more spells that are similar in quality to minions of the same cost, like Flamecannon.
Right now with the joust cards we've seen so far there's not enough quantity and quality in the jousters to motivate you to skew your whole deck towards it. But I think we might see more joust cards.
I really don't think the joust cards will end up being cards you just hurl into control decks with no deckbuilding consideration though. In Magic, "reveal a random card of your deck and check it for a certain quality" has always resulted in totally building around the card or totally refusing to use it at all. Vampire Nocturnus, Polymorph, Cascade, Delver of Secrets, and Clone Shell all turned out that way (Clone Shell counting as an example of "totally refusing to use this in a competitive deck at all", it was not good enough).
Even though this mechanic seems somewhat less affected by the buff trigger than those other random reveals, the way they are designed so far makes it difficult to play the cards in control unless you know who's going to win the joust. If you have 6 mana, a Master Jouster, a Sludge Belcher, and a Cairne Bloodhoof in hand, you're going to play Sludge Belcher if you need taunt to stay alive, and Cairne Bloodhoof if you need to generate long term advantage but your health total is ok. And if that's how you're going to end up playing your deck anyway, why not run a Piloted Shredder or Shieldmaiden instead at that point? Restoring health to hero and buffing to enough stats to win a trade are also things where you need to know the outcome in order to play the card over something else in your hand. The only kind of effect I can think of where you could be ok to joust-n-pray is drawing cards, which is what Skeleton Knight does, but they were mega cautious with him so the card you draw is pretty terrible (needed at least 5 health to be worth a serious look).