At the close of his four year rookie deal he couldn't get a multi year offer from anyone... I'd say it makes him a bust. Sometimes a bust can recover their career, but they were still a draft bust if that is how things played out for the team that took them.
And while his effort is certainly better, leading to less games where he is invisible, he is still an atrocious team defender who constantly is in the wrong position and, according to this Zach Lowe article, the worst player in the entire league on post up opportunities.
http://www.espn.com/nba/story/_/id/...-things-like-including-houston-chris-paul-nba
Despite the big statistical nights he has had I still would not consider offering Len a multi-year deal. IMO he is still essentially a net negative for the team and that he only finally started to show some hustle when he career was on a fast track for the euroleague makes me really weary that he'd return to his old "invisible man" habits if he had a long term deal.