Late game Viper with tank items and a scepter is just ridiculous... 80% attack and move speed slow with roughly 50% uptime that goes through BKB and has a greater than average cast range? Crazy.
Why'd the pros stop using him? Especially with them trending towards aggressive playstyles, you'd think he'd be a popular pick. Hell, stick him mid and he'll counter the shit out of that first-pick TA.