I saw very interesting viper build and it was very good i mean the guy is pure pro.He made ghost scepter and dagon and wth combination of ultimate it did very well.Well they were pawning us hard so he realised it will be fast game and he can send money on some core items and he got dagon which he made 5,6 more kills
Viper can have very interesting build ,suggested vangard if you are not doing well and than get some critical and atack speed...viper is all that...and after you can investage with exotic items like this guy did with dagon or etheral blade