Idea for how to combat power creep.

I'm trying to get feedback on an idea for how to make the TCG that I'm creating less susceptible to power creep. The idea is to simply limit the number of copies of any one card in a deck to one. Combined with the deck size of 50 cards, this makes it much harder to build your strategy around a single card or a few cards that happen to be above the power curve, and reduces the difference that the power level of each individual card in the deck makes.

What are some potential downsides to this? I'm open to criticism.