Javelins are 8" range poisoned attacks the same as blowpipes. Correct? Is that not why I see them equipped with shields for close combat and hordes?
They're both 12", not 8", but I'm not sure what your question is. If you're asking what their relative benefits are, and why people take one over the other, there are already several threads about it. Just give it a search.
This will probably answer your questions about Jav vs Blowpipe. http://www.lustria-online.com/viewtopic.php?f=15&t=8082