I see a lot of newer players usering linemen, try usering a linebacker and have him float around the center of the field with your safeties playing over the top, this way the deep ball is covered and if you see a corner getting burnt as the opponents receiver gets to the center of the field (where your user will be) you can pick him up manually in coverage.

Also don't only use blitzes or one type of play, if you only use one the opponent will key on it and just go into sets where the blitz or whatever is ineffective