So, I did a bit of math, and I have determined that Hit The Road Jack definitely needs a buff.
With a completely un-fixed deck, the absolute maximum XMult HTRJ could reach is 3X. This sounds like it makes sense, because most Uncommon Jokers have a basic 3XMult if you can fulfill their condition- but when you think about how hard it is to set this up, suddenly, things become a bit less, uh, good. Discards are typically used to dig through decks, and since there are only four jacks per deck (excluding erratic), you're more than likely to have already used all of your Discards before even seeing more than one Jack- unless you use your Hands to dig, which is a risky play for not much reward. The chance of drawing a Jack in an unfixed deck is 4/52, or 1/13, which isn't worth it.
What about a fixed deck, though? Assuming you want to make a Jack-Based build, much of your deck will be changed using Hanged Men and Deaths. Typically, I reach ante 8 on most of my runs where I actively try to shrink my deck with about 40 to 48 cards. Assuming the number of Jacks in the deck has doubled, the chance of each individual card drawn being a Jack is 1/5 to 1/6. Much better, but still not great, since the maximum XMult if you manage to draw every Jack is 5X- but again, the chance of drawing every Jack and being able to discard them is still low, even if you use some hands.
Therefore, I propose Hit The Road Jack should get a buff of some kind. Raising the gain from 0.5XMult to 0.75X or even straight up 1.0X would suddenly make this Joker go from practically useless to situationally powerful and something worth potentially building a deck around.
This came to me when I was watching a Roffle Lite video about the all-10-of-Spades Erratic Deck. He turned the whole thing into Jacks, and had five discards, and briefly got a Hit The Road Jack, but sold it in favor of a Hanging Chad.
TLDR Hit the Road Jack is too difficult to use for too little reward, so buff it to 0.75X or 1X.