
At first glance, Leo looks like an automatic-include in every Rogue deck. His power, granting an extra action every turn, is a huge benefit. Unlike things like "Skids" O'Toole's ability, it costs nothing per turn, and unlike Daisy Walker, the action isn't restricted. That extra action is fantastic.
The thing is, so is his cost. Make no mistake, a card draw, an action to play, and 6 resources is big. He is the most expensive card in the Core Set. He only has one - so he's not that useful for skill checks. Even the upgraded Leo De Luca, with it's reduction in cost, he's still the (equal) most expensive card in the game.
So... is he worth using?
If you can get him out early and keep him through the game, Leo De Luca is a huge boon. He will, over time, repay that huge initial cost. I've had games where this card has been the entire margin of victory. When you're racing against the clock, he can be brilliant.
If you don't get him out early, though, he's a wasted card. Late in the game he's too expensive to be worth the investment. For example, 6 resources would pay for 3 additional turns with additional actions for "Skids" O'Toole, and you'd still be better off.
And so I find that I end up either taking 2 copies of him (and no other allies) - to try to draw him in setup or as a Mulligan, so I can get him played on the first turn - or I take none, and instead use other allies. It's very much a "Leo" or "Not Leo" strategy.
Rogues can also have access to Cat Burglar, which is excellent, and "Skids" O'Toole also has access to allies like Beat Cop. Both these cards are very good, and make Leo De Luca look like less of an automatic choice - and more of a considered one.