I just took about six or seven tries to get the Hylian Shield in Hero Mode. I didn't prepare with Guardian Potion or anything; I wasn't that desperate yet.
I started with Demise (just for fun) three times. Twice, the second boss was the final Imprisoned battle.
I then started with Tentalus three or four times. On all but one of the tries, the second boss was the first Ghirahim battle.
I find these coincidences a bit too unlikely to be due to random chance. Is there a pattern to the order of boss battles depending on which one you pick first? Perhaps for each boss, there are more and less likely bosses that follow that one? Is it perhaps possible to choose a boss that will more likely yield an easy sequence if you're only going for four or eight victories?