[Sunderfury]

July 1999 post, kind of sketchy but makes mention that disease dots were originally meant to only stop the healing process.

I can only attest to one of the changes to the poison/disease DOT spells
(since my shaman is currently only level 8), but the good news is the one
change I can report is a nice one for low level shamans.
Sicken now actually does damage to your enemies instead of simply halting
the healing process (which I actually think did more harm than good when
dealing with runners). For my shaman it did an initial 8 damage and then 1
damage per tick up to a total of 31 points of damage. I was able to kill
polar bear cubs with two casts of the spell without using any additional
casts

June 1999 post of disease stopping mob regen

Disease Cloud, besides doing 5 pts of damage per cast, diseases your
enemy and prevents it from healing normally.

Disease Cloud does 5 damage and
also diseases the monster, meaning they don't regen hp during the battle.

I think the real power of disease cloud is that it stops a mob from healing
itself. True, the 5 points of damage is almost nothing, but a high-level mob
can regenerate many times that number during the course of the fight. And it
only costs a measly 5 (or 10, I can't remember) mana.

November 1999 post

When there's no druid around to help me out, I pull with sicken to
kill regen and do maybe 30 damage, hit it with tainted breath before
it gets to me, melee, one more tainted breath when the first runs
out, melee, and it dies. This works up to yellow crocs no sweat. Reds
I can kite down to 66% HP then fight, but they're more trouble than
they're worth.

Damn that seems such a long time ago but at level 16 I spent most of the
level in Oasis (seemed like the thing to do) and I used to DD crocs. could
take all of them except the Deepwater Crocs. Deepwater Caimans I'd
sometimes need to zone so I avoided.

Pretty inefficient but it was another 3 levels before anyone told me about
DoT spells...

April 2001 post, seems to mention high level and low level dot can both negate mob regen.

Best Advice I can give...which works for me is the Root/dot/dot method.
Start with root. Head back to maximun range and cast your disease dot.
THAT stops them from healing back some of the damage over time. Careful
though, because at higher lvls your DOT tends to break Root on contact.
Which is why you head to the maximum range to cast. If Root breaks you
should be able to recast before getting hit. If not, take the hit and get
the spell off. Go ahead and med while Root/DoTs are in effect. Remeber to
Have regen going on you at all times...and Canni to keep a ready supply of
mana. Always try to sit far enough away that when root breaks you have time
to stand and cast it again before getting hit. If you run low on
Mana...just keep rooting the MoB and med up. If need be...mem a lower lvl
disease buff to keep the mob from healing.