A few detailed Necro questions
 

1) If your pet triples (not counting kick/bash), does that mean he is successfully dual wielding without weapons?

2) What's the difference between the lifetap DoT line and lifetap? The mana->hp ratio always seems the same and the negative mods are about the same (other than one is instant and one is not)?

1. Yes.

2. The DoT draws less aggro.

2. and the DoT doesn't break root and you can cast other spells while still being healed instead of casting lifetabs over and over.

1) Yes

2)
Instant Taps:
lvl 29 Spirit tap has just slightly over a 1:1 Damage/Heal to Mana ratio
lvl 39 Drain Spirit has a 1.2:1 D/H to M ratio
lvl 49 Drain soul has a 1.5:1 D/H to M ratio
lvl 54 Deflux is a 1.6:1 D/H to M ratio
Lvl 59 Touch of Night has a 1.77 D/H to M ratio

Tap DoTs;
lvl 29 Vampiric Curse has a 1.3:1 Damage/Heal to Mana ratio
lvl 49 Bond of Death has a 2:1 d/h to m ratio
lvl 57 Vexing Mordinia has a 2.22:1 d/h to m ratio (although you have to be really low on health or have a lot of +hp gear to get its full effect).

At equal levels the ratio on the DoTs is signifcantly better. The period in lifetap dots between 39 and 49 (realistically more like lvl 44 when Drain Spirit does full damage) where there is no upgrade makes them less desirable. Once you get it, BoD will always be a better spell to cast for health-regain purposes in a controlled non-emergency setting. Vexing is even better, if you happen to find yourself 1k below your max hp and not at immediate risk of dying.

I left out the stuff below level 29 because they suck pretty bad.

Also forgot to ask - what tricks can be done with a circlet of shadow?

can stand up and invis instantly before mobs aggro you

The first pet to dual wield w/o weaps is the max level pet with the lvl 39 pet spell.

I believe the DOT will also continue to siphon life after the mob has died if it has not run it's course.

and you can instantly break charm.

that's true. It's basically the same with a lifetab which will also heal for full even if the mob is at 1 hp.

duel wizard pal, cast hp drain on eye of zomm

don't have to duel for this on red