This goes to show that it's impossible to please everyone since people have different preferences. The people that champion having around 10+ Batman characters are usually the ones to complain about lesser known ones making the cut(or "nobodies" as some like to call them). And vice versa.
And regardless of originating in a Batman comic, I don't think Deadshot should count as a Batman character. For one thing, he makes up for less than 1 percent of Batman stories and his history with Batman seems to have been wiped out. And also Wolverine first appeared in the Hulk's comics, but he's clearly an X-men character. Sabretooth is an X-men/Wolverine villain, but he spent his early appearances fighting Iron Fist and Luke Cage.