If they're more productive and you can afford it, why not? That pretty much goes for anything in business. Trying put put a time-clock and billable hours on creativity is a waste. I would never pay an author of a book based on how many pages they write.
There are plenty of creative pairs/teams that make more than they both can individually. Movies, books, music, scripts are often created by more than one person. You may find your creative team puts in more productive hours because they enjoy working together. Xtreme programming advocates pair-programming. The quality of their initial work goes up, fixing bugs later costs more, negative effects of turnover are limited, communication is increased.
Not all creative people play well with others. If true creativity is what you need, try to avoid everything that gets in the way. That's always possible. No reason you can't try it and measure your results. Please share your results.