This doesn't have much to do with your method, but I think it's an interesting alternative that moves in the opposite direction (tougher PCs). Basically, if you're not happy with your hp roll, you can reroll with the next lower die. In other words, let's say you're a fighter, and you roll your d10 for hp, and it comes up 3. That sucks, so you reroll it with a d8... which rolls 2. Damn, it's not your day today. So you reroll again with a d6, which comes up 5. Well, it's not gonna get better than that with a d4, so you keep it.