Viper DPS Carry (DoT Heavy Flying Guy)

Have to agree about not needing a Hood, or even Vanguard. If you're being focused that hard when playing Viper, then you're doing something wrong. With a range as big as his, you shouldn't be on the front lines. If the whole enemy team decides they need to focus you, Shadow Blade and illusions are more than sufficient to take the heat off so you can reposition. If you're relying on tanky items to survive, then you're only delaying the inevitable.

If you play Viper right, he should be standing back and not being focused on. This means a hood wouldn't be needed and a Butterfly would help his DPS greatly.

Where da Hood at?

Not a bad base for a Viper guide you've got there. Here is some feedback thus far:

Item Build:
Consider opting for a Ring of Aquilas and a Magick Stick instead of 2x Wraith Bands. RoA builds out of a Wraith Band + Ring of Basilus and is an extremely good item for ranged AGI heroes like Viper, providing DPS, bulk and a bit of Mana regen for Poison Attack. Magic Stick is a strong option because it builds out of 3x Branches and has an exceptionally useful active for its cost.

Thanks to Corrosive Skin, Radiance is an interesting choice on Viper, but your build timing is off. Radiance is not a late-game item; instead, as a source of constant, flat AoE magic damage, it is more effective the earlier you get it. If you are going to get Radiance on Viper, you should get it early/mid game, preferably if you are snowballing hard.

Shadow Blade/Manta Style/Monkey King Bar is a nice core, however. Butterfly/Heart/Assault Cuirass make excellent luxuries in games that just won't end. Don't forget to tell people to carry TP Scrolls as well; TPs are very important for Viper for both counter ganking/possibly escaping ganks.

Skill Build:
Your skill build is a bit scattered; I prefer:
Q/W/Q/E/Q/R/W/W/W/E/R/E/E/Q/Stats/R

Poison Attack is rushed but left at Rank 3 due to it's linear damage/slow scaling and cooldown scaling of 4/3/0/0. Nethertoxin is maxed first over Corrosive Skin due to it's stronger scaling per point (32/64/96/128 versus 10/15/20/25%). A rank of Corrosive Skin is taken at Level 2/4 to take advantage of it's Rank 1 strength.

Needs more Hood.