VICTORY! STORM DRAGONS ARE SUPERIOR!
Long story short I spent a lot of time and effort fixing a cobbler box... tftp was working fine but any pxeboot attempt failed.
Devs responsible for configuring cobbler kept blaming it on networking.. finally I go rooting around and every boot attempt is failing on read request for pxelinux.0... enable bulk transfers and suddenly it works! :D
More evidence to pile of "I don't trust this dev team"