I was just followin the build on some guide. I don't know any other substitute to give me more HP
yeah vanguard is also still put in the recommended items for a lot of heroes but honestly you should never build it.
the "70% block" since it is random is more like 60.1% and since you are ranged as viper it only blocks 20 dmg even with the 60% it's more like 24 dmg block when you factor in it missing for melee.
compare that to a simple poor mans shield, inexpensive item that blocks 100% of the time for 20 dmg or 10 for ranged and you got a useless item that should never be built. Poor mans shield also gives you 6 dmg and .84 armor on agi heroes. You factor everything in and vanguard is barely ahead of poor mans shield in damage reduction for over 4 times the gold.
It does give you health but you should be building bkb on viper and power treads early to cover the health. Vanguard is just useless 1 more hp regen than a regular ring of health, a crappy block, only good thing is 250 health but you are spending a good chunk of gold on it.
edit. that's all just in general don't build poor mans shield on viper either lol