The main problem is that the item completes itself. While the bleed allows to negate 30% of the incoming damages but the life steal provided by the item allows to counter the bleed and thus survive, especially if ADCs use it since they heal a huge amount of health. The best way to fix the problem would be to separate Death Dance into two distinct items; one having the lifesteal passive and the other one having the bleed.
By "him" I'm assuming you mean 
. DD provides a little extra tankiness sure but that's kind of the point. And by buying that instead of say another crit item early on you miss out on a lot of damage. I think it is fine the way it is.
yeah but the ADC will cry that "its not damage reduction" becuase they have no concept of burst damage taking evey skill in your kit and aftewards leaving you defenseless, it taking 143% lethal damage to one shot someone with 
and that if you don't one shot them... they life steal back.. because you used who your damn combo.
oh and not to mention any champion that has part of their combo deals more damage based on missing HP. which of course gets hit TWICE becuase they have 30% more hp when that skill calculates its damage.
i mean no one is going to argue that if you are just trading.. and they arn't going to take fatal damage.. the bleed is fine. Then its just a "bleed" with no damage reduction.
but it becomes and issue when the said 30% damage over time keeps them alive from what otherwise would have been fatal damage.
and thats why bumping it from 15% to 30% and adding 10 AD completely broke the item
imo the item would be fine if they just brought it back down to 15% reduction
