I don't really mind Duskblade, but you need to delay the powerspike by 3-5 minutes.
Throw in a Pickaxe and give it a bit more AD. Squishies just need enough time to finish a Seeker's or something.
The Duskblade spike comes right before even 1-item champions get to reach their first big powerspike. IF you don't spike at gunblade/DD/BotRK you're just dead without the ability to trade back. Even then, Duskblade is about 700-800g cheaper than any of those.