In my case, a strong/hard 10 miler comes down to Half-Marathon pace + 20 seconds.
I'm quite slower than you (1:26 half), so 6:35 HMP + 20 = 6:55 10-mile tempo.
Or at 6:15 10k pace that's 10k + 40 seconds.
Am I running them too hard? Those tend to be my harder runs and replace the traditional long run, especially on low mileage (40-50mpw). I found that they build strength like no other runs
Also doing 12 mile tempos, tend to be be slower (HMP+30), and 16 mile long runs when training for a marathon at HMP+50 or so.
Curious to hear about you.