Nothing bad about virtuoso, on the contrary, they are a prime infrastructure provider (Except maybe their trademark SPARQL query: "select distinct ?Concept where {[] a ?Concept}" ;). But I personally think that replacing the current WDS with virtuoso would be a bad idea. Not from a performance perspective, but more from the signal it gives. If indeed as you state virtuoso is the only viable solution in the field, this field is nothing more than a niche. We really need more competition to get things done.  

Since both DBpedia and UniProt are indeed already running on Virtuoso - where it is doing a prime job -, having Wikidata running on another vendor's infrastructure does provide us with the so needed benchmark. The benchmark seems to be telling some of us already that there is room for other alternatives. So it is fulfilling its benchmarks role.

Is there really no room for improvement with Blazegraph? How about graphDB?