That's not to say you did anything wrong - it's possible your specific set-up wouldn't work. But many agencies do not know how to do it.
i think facebook user has a different expectation then google. i know some companies first hand that had great expirience with b2c, i never meet some that did great in b2b.
maybe if our focus was more on creating a community around a common thema, and then do brand building or so, it could work as a secondary generator of leads, but for pure,i pay for an ad and the goal is to get an conversation it was not that great.
so if you could write more about what does work it would be great because only relaying on adwords and always increasing cpc is not that appealing.