There is also the fact that a short time before they showed up to get beaten, Oliver specifically ordered them to stay in Star City.
I want to take your comment about Katie Cassidy a bit further. The problem started way back in season one. Very early on in the season, when Laurel saved Oliver and Tommy in Mas's club, they showed that she could at least handle herself in a fight. But then they never showcased those skills again. In season 2, they made her a drunk and an addict who was incapable of taking care of herself. and then in Season 3, they had her take the mantle from someone who was very popular in her own right and who was killed off for BS reasons. And then they showed that she really WASN'T skilled enough to take over. But due to the way time passes on this show, it felt like she was getting too good too fast. And she never did move with the confidence of Caity Lotz.