I personally didn't have to farm vials too much, and I only ended up having to do it with two bosses in the DLC, which adds to my point. Most people end up having to farm vials when they're up against a boss because you're up a against a wall that isn't giving you any echoes or blood vials drops. When that is the case, the solution is not as simple as spending your left over echoes after leveling, you have no echoes to spend. its a step back from a system that already worked quite well such as with the estus. When farming can end up as the only means to get health items in a punishing game where you're constantly healing, I consider that a flaw.
As for the bosses, the only ones I consider actually good in the second half are Gehrman and Logarius. Ebrietas and the Wet Nurse are another 'get behind them' boss that is quite prevalent in BB. Only in their case they're completely helpless when you do it. Amygdala I wouldn't consider bad, but I wasn't impressed by it, similar to the Shadows of Yharnam. Then you have the likes of Rom, One Reborn, Micolash, Witches of Hemwick, and the Moon Presence, which are either very mediocre or bad. I don't consider the DLC bosses part of the second half of the game, because they're not part of the base game. The OP's experience clearly reflects this.
As I said though, some of these issues didn't stop me from loving the game as much as I do, to the point of considering it my own personal favorite game. But this game isn't the second coming of games as GAF makes it out to be.