So your argument is that the vial system is good because it rewards you for wasting time farming vials and souls, and punishes you for just trying to beat bosses over and over? It's bad game design. Your second point then counteracts your first one, since a greater emphasis on regaining health through attacking would exist if you reduced the number of available blood vials to Estus-levels
Compared to the Estus system the blood vials do two things:
- Place reliance on the amount of consumables you have rather than your own skill during boss battles (since you can carry so many vials if you put in the time)
- When the player actually faces a difficult fight or area, they have to backtrack and engage in tedious busywork.
It's a solid lose-lose situation. It makes the game easier in all the ways you don't want, but also makes it more difficult in the worst possible way (grinding for vials). It's not like this should ruin the game for anybody, but let's not pretend its not a huge step back after Dark Souls.
It's not a second phase lol. Just do it.