GSA is working better than for a long while with me - Joomla update and all.
Have you looked at the chart for your links, see where their coming from? Almost all these problems are down to a single platform that's changed and GSA is not working (At the current Moment)
As others have said too, proxies, captcha and if you're on a rubbish VPS will all hurt.
I get about 30 - 60 VPM and it pretty much does that all day which suits me fine for my projects.