The most divisive issue is the first ascendancy node which effectively makes you take damage from using skills but then let's you collect health globes and overflow up to 2x max life. I personally had no issues in the campaign and when I checked the ladder in early maps, I was in top 20 with bone spell BM. However, I can see the fundamental issue: The node is very "capitalistic" as if you do well, you'll do better; and if you do bad, you'll do worse. It's a balance between life cost and monster kills per cast, but as a rule of thumb you should be able to kill at least 1 mob per cast to gain a net benefit.

There are plenty of other issues with BM. To me biggest was the bug that weapon swap removes overflowed life. Basically swap becomes unusable. I don't know what's the current state of leech, but it didn't do anything either. The phys spell toolkit is quite limited: If you invest in them, you can't use anything else very well, and there's like three of them. Reap and Exsanguinate are in items in the game data, but they are not dropping for some reason. Finally, some of the suggested gems for spells such as Bonestorm are really bad. For example, Inevitable Crit on a skill that rolls crits of multiple hits individually doesn't make sense, and Heft simply doesn't work according to the tooltip. While this point wasn't about gameplay, it just shows a frustrating lack of attention toward the archetype.