"Why is it that there are far more Senior positions available on Game Job boards? Is it due to a major lack of experience on AAA titles or a major crackdown in the HR department?"
This is something that has been common in the Games Industry for as long as I can remember. Game companies get lots of resumes all the time for jobs that they post and a good percentage of those applicants are often under qualified for what they are applying for.
Imagine how many more applicants they would get if they actually posted an entry level position that requires no game development experience? This coupled with the fact that in today's industry with so many schools around we finally have avenues to find out who the ideal candidates are instead of going wide to the general public.
I don't remember ever seeing an entry-level position being advertised anywhere but the truth is that they are often there if the right person shows up. I got my second job by contacting someone I had met at GDC to just ask if there was anything available, even though no Design positions were listed on the site. He brought me in and hired me shortly after...so it never hurts to ask! Send in your resume along with work examples to all the places you're interested in and maybe they'll give you a look.
Most of these positions that I have seen filled come from recommendations of current employees who know of a tester or recent game development graduate that they think will be a good fit. Personally, I contact Full Sail any time that I have something available to see if any recent top of the class grads are looking for work. So, who you know still makes a huge difference in this industry.
I hope this helps and keep the questions coming everyone!