The faster your PR, the harder it is to do 800s at that speed.
If you are in any type of good shape, 3 reps is tough, 4 is REALLY tough. Newbies would struggle with this workout too, but It honestly doesn't hurt them that bad. It seems counterintuitive, but newbies haven't really touched what they are capable of so once they've done a few rep sessions, doing 800s at mile pace isn't too hard.
I was in the Army after high school and thought I knew how to train. I was on my company running team, so I got out of normal PT most of the time. I did a ton of hill repeats and intense type of stuff on my own. I really wasn't that fast at the time, but I was fast relative to the other guys in my unit. One workout was 4 x 800 with 800 easy jog between reps. I was running 2:30s, but probably would have had a hard time running 4:55.
When I was in college, I would have had a tough time running 4 x 800 at mile pace though
It also depends on if you're a speed type runner or endurance type runner. A speed type guy will have a much easier time with running 800s at mile race pace.
In my coaching now, I rarely use reps longer than 600 at mile pace. The exception to this is with strong 800m types who are already pretty fit. I actually have them do 3 x 800 at 90% of PR 800 pace with up to 15 minutes recovery. (so a 2:00 guy would do his 800s in 2:12) This works out to a bit faster than mile PR pace usually, but it's a great session. For you, however, probably not what you are looking for in the 5k 10k road training.