Sure, there is a limitation to this card, making it only useful for champions. But we have seen a number of champions show up recently that can fulfill this requirement.
The 'Vehicle' designation suggests there will be some kind of future limitation that we have yet to encounter.
All of that said, this is a frankly amazing card. Full stop. Incredible. Champions is different than several other cost-based card games, in that every card is always a resource. In a game like M:tG, swapping two cards for two more cards is only marginally beneficial, since that is a game that requires you to hold cards for extended periods to best utilize their effects. Also, you die when your deck runs out.
But Champions is all about turnover. You use cards to pay for cards, so there's no issue with churning through your deck looking for the best cards and combos, running through your 40 cards numerous times. A Support card that lets you cycle two extra cards each turn in search of the pivotal cards for your strategy? Delicious.
As opposed to Avenger's Mansion, it doesn't provide you with resources on top of deck-plumbing. But it DOES dig an extra card deeper into your deck, for two less cost. So you won't get that extra resource to play two 2ER cards, but you absolutely will have a better chance of finding the actual cards you want.
In my opinion, this kicks the literal crap out of Avenger's Mansion. You can argue that it never pays for itself like AM does, but the accelerated search through your deck for your best cards far and away makes up for it.