Most OP hero

Probably because in the last competitive games with Warlock that I've watched he was being played in mid lane as a farming Hero, thus making his autoattacks and items a lot scarier than a slow (that's not completely true, but I think this is what the team running the mid Warlock probably thought). Plus, you need to be very close to the enemies so you need a Blink Dagger, Force Staff or a good initiation before yours and the channeling of your Upheaval is easily interruptable.

I'd rather run him as a full support and go for a Upheaval- Fatal Bonds skill build, but since a ministun can break the combo it's a very situational pick for safe lanes. Otherwise, you can opt for a Blink Dagger + Black King Bar skill build in mid lane even though it requires a good amount of farm.

Still, I think a Magnus/ Treant Protector/ Tidehunter/ Puck + Undying combo is more reliable and requires very flexible Heroes: most of the time it even has better results.

In my experience with the DotA scene:

Viper is an excellent Pub smasher if the team continuously tries to engage you, because that's exactly what he is build for. If you leave him alone and farm up (or gank him to kingdom come) first, he'll be crushed.

Drow Ranger you are forced to gank if you don't want to be crushed late game, but if you just carry some dust or sentries it's pretty simple to take her down.

Same rule applies to Sniper, because both him and drow usually go Shadow Blade.

Special mention does go out to Bloodseeker though. Noob and stupid hero that would never be picked up in a legit match, of course, but he can really take control of a pub match if you give him kills early.

Bloodseeker isn't a stupid hero.H's considered one of the greatest chasers in the game with his helpful passive.

He's **** tier.What is the point of chasing if you can just teleport away from him?