Of all the "Launcher" type clients I've had to put up with, Battle.net is the LEAST annoying, IMHO. I am using it to play D3 and OW on a laptop with integrated graphics (granted it is almost brand new laptop and has Intel's latest/greatest graphics solution) and I see no real performance hit.
I also LOVE some of the extra features the client has, like Live Streaming directly to Facebook Live! All I had to do was link my Facebook account and press F1 from inside any game launched from the client and it uses my webcam to show me in the lower left corner as it posts my game play in real time to FB Live! There is a noticeable performance hit when streaming but really how much can I ask of a laptop?!?!?
I have ZERO problems with Battle.net and since Blizzard makes like 80% of all the games I love, I use it every day.