Nah. Completely disagree with this dude's point. Roy's been mixing it up with very little training and regardless of Diggle's training, he's been shown to be outclassed constantly as well (which is a disservice to Diggle but still stands).
Let's also not forget that more than half of the villains are nothing more than Civilians as well. I mean how do we explain Cupid holding her own against Arrow? What years of training in hand to hand and archery did she have? At some point, as a viewer, you just have to accept that there's going to be a level of fantastic, whether it be Mirakuru fueled baddies or characters with very little real-time training having the near abilities of Arrow or Merlyn, who have extensive training.
This dude's opinion really does come from a place of just hating the character so much that there's no way that the writers could ever have redeemed her properly in his eyes. I mean the dude had Stephen Amell on the After Show and still had the nerve to completely trash her character in front of him. Dude's a lost cause and it's probably better for all parties that he's stopped watching and will stop participating in that After Show.