The sludge might be a bit of an issue but I did those on my 5x Paladin group at level (yeah, yeah, not classic etc. etc. etc.).
The deathwalker ghosts are really slow. The way I dealt with those was lining everyone up facing the same direction and then just walk backwards when they start dying. If you're doing an AoE group, they all kinda die about the same time so it makes things easier (less backing up).
/agree
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