User blog comment:Supp0rt4n00bz/Welcome to the League of Hydra!/@comment-9048637-20131219180210

People rush Hydra from Tiamat because an early Vampiric Sceptre is nice on any AD champ who plans to eventually build lifesteal anyway, and once you have both Tiamat and Vamp Scythe, you're paying 600G for 25AD (the same as a Pickaxe, which is 875G), 2% extra lifesteal and space in your inventory. Yeah, if you're doing well and you never felt the need for the early Rad Scythe, then tanking straight from Tiamat to Hydra is a little questionable, but if you already have both, then the upgrade is actually very well worth it.