If a team can tank long enough in any team fight while Death Prophet stands back, that team can force tower/barracks losses, even if they totally lose the team fights. As long as Death Prophet stays alive for her ult to dive a tower, her team did its job. The kill disparity becomes completely irrelevant just because you cannot do anything to stop the push from her ult.
This has been demonstrated in a few competitive games this year, most notably Na'Vi vs. Darer in which Darer won through protecting Death Prophet, though in general the team fighting seemed to be largely in Na'Vi's control. In other games against Darer where Death Prophet was not picked, it was more or less completely one-sided for Na'Vi.
I know some people might think this is exaggerating, but I'd consider Death Prophet a first-round ban, in the same tier as Nature's Prophet and Leshrac. If she is protected, her team can easily force a loss just by fighting near towers and keeping Death Prophet up during her ultimate.…
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