Yeah I think it's more accurate to say he's like Ricky Gervais playing Brent, which is not quite the same thing as being Brent. He's using Gervais' acting style and mannerisms while playing Brent. However, it can easily be seen as him using Brent's mannerisms, which it is being seen as, and this is the problem. I'd blame the writers for this more than the actor, as it seems like G and/or M have indeed used the David Brent template for creating 'Warwick Davis'.
When his responses and dialogue are very similar to Brent's, then what chance has Davis got of not looking like a short David Brent? An oversight or mistake by the writers? It certainly seems to be causing more discussion than anything else in the show, which is a shame, as it is very funny in places.