Previous related applications (mostly written >5 years ago) were written in high performance programming languages like C/C++
I have to say in advance that I've never did some serious Haskell programming, but I don't think this statement is true. C is still the language of choice for this kind of tools. If you are capable of writing a high performance string matching tool, it will be quite trivial for you to make it multi-threaded. The guys in our department worked really hard for over a year on a very efficient suffix array tool, parallelizing it was a matter of weeks. Another reason to choose "high performance programming languages" when it comes to high performance computing is simply memory. I know RAM is cheep these days, but suffix arrays are demanding. For example if you want to search in the complete human genome, you'll need far more than 8gigs RAM with the most efficient suffix array implementations available.