Reiko, it's not _that_ unusual. the stage 4 death wa unfortunate and probably more of a one-time thing.
the stage 6 death is actually common and shouldn't be pondered about. you need to survive 2:30 minutes in the first round which is pretty tough.
now, stage 7 starts with 2:30 or 3:00 minutes to win. I have no idea, I never survived long enough for either :V and drops to around 2 minutes after the first death for round 2 and 3. if you don't play the game regularly, 2 minutes is a lot. and the dodging and stuff picks up from stage 7 onwards, too. unless I got ridiculously lucky, I never won against yuka (I play komachi, whose stage 7 is yuka) in the first round, for instance. if you play the game for a while, you'll find yourself reaching eiki pretty quickly. Komachi and eiki are pretty tough, though. so good luck.
that is all under the assumption that the K.O times are the same in hard, of course.