His workrate isn't low though because he's lazy. He isn't.
He's very much like Torres in that he expects his team mates to put him through on goal and spends a lot of time high up the pitch finding space and riding on the shoulder of defenders.
Gerrard allowed Torres to do this at pool and now Mata is accomodating Torres' playing style at Chelsea.
Thing though with Aguero, this is why he's always been a second striker. Playing with two different types of strikers is beneficial because you can reap all the offensive rewards. Right now we have a striker that stays high up the pitch creating space for others, giving defenders something to worry about, while the other striker contribute more in the build up.
We're used to Tevez and we've not really had a striker of Aguero's playing style, so as fans we miss that workrate. But Aguero ain't no headless chicken as his off the ball movement is very intelligent. His game will really improve even more, at 23 years old, it just has to, and it will.