You're booting off a 5400 RPM TB drive, it's going to be slow as shit. Get a very small 10k RPM or atleast a 7k RPM for booting and keep your TB for space.
Even though it is 5400 RPM, the platters are 500GB in size. This means it is still crazyfast and has higher average transfer speeds than most drives out there. Most people only look at RPM and cache and don't take platter size into account. Take my 2 spinpoint drives for example, identical in every way except platter density; one is 320GB per platter whilst the other is 500GB. 320 averages 85-90 MB/s read, 500GB averages 120-130 MB/s.