All of these "inconsistencies" have been explained. It is up to you whether you've actually read them - in quest text, novels, or other sources.
McNeil's example of Varimathras for example-- it was an act, to make his placement at her side more believable.
The Fel is terribly powerful on its own, it is not yet clear wheter it can truly, fully, corrupt a Dreadlord (leading to an alignment switch from Death to Disorder). This has been purposefully kept vague of course, to be decided by blizzard when the question becomes relevant enough for the plot.
I'd also recommend you take that last sentence and apply it to a lot of things you think are inconsistencies, but are instead just open threads that Blizzard has left open purposefully, to pick up whenever they wanna tell something cool for the plot
Indeed. Repeatedly it has been stated that a death in the Shadowlands is Oblivion. Non-existence. A removal of your everything, from everything.
But smoothbrains can't comprehend words longer than 2 syllables so of course it's "uhhh death is DEATH but death in DEATH is DEATHh?!"