they can be used on 2 handers an as far as im aware, they go off a proc per minute rate i.e. it makes no difference how slow the weapon is, it procs a certain amount each minute of combat. as ive only heard scraps about this, i cant really confirm it, maybe someone can.
as far as lifestealing goes, if youve got the cash, go for crusader. LS procs approximately 4 times more than crusader but crusader will heal for half of lifestealings total at minimum and has the potential to beat it. however, seeing as it can only do 125 at max, this is unlikely but still a potential. rogues duel wielding these babies can get alot of hp return but this isnt the case in this thread
unholy weapon lowers damage taken by 15 (simpler way of putting it :P) and i would say is more class dependant. although to be using a 2 handed axe you have to be a mail / plate wearer, unholy weapon is a bit daft on cloth wearers. youre taking so much damage that 15 aint gonna help. if youre a shammy, unless youre soloing, youre not likely to be getting hit (dependant on the tanks skill of course) so causing a mob to hit for less isnt all that important for you. if youre a tank however, that damage reduction may be small, but it may be enough to save your life. against big hitting 2 hander MS mobs, its useless. 2000 - 15 isnt gonna help. if its against fast hitting but low damage mobs (like gelihast in BFD as a low level but well known example) then 15 is gonna be a real pain for them. they do bugger all damage in the first place so that 15 is gonna reduce it significantly.
crusader is a perfect tank proc. in anyones eyes, +100 is a significant boost, especially at lower levels. this means increased damage which means increased agro levels, this is nifty for a tank. we have yet to do some testing but me and my warrior friend are pretty sure the proc itself causes agro. not sure about this though so if anyone could confirm it...
anyway, healing generally means agro so youre getting yourself that extra hate. the extra 100 strength allows for plenty more damage and so even more hate/ although the proc rate is low, the actual proc of lasting for 15 secs is a reasonably lengthy one compared to some weapon procs.
so yeah, my advice (im a 300 enchanter so of course im gonna try and sell this one..) would be to go for crusader / unholy if you feel that youre warrior is gonna be taking more damage than normal (duel wielding for example or being 2 hander in this case so no shield), crusader / unholy for hunters because the healing proc from crusader may just be enough to save your skin and because hunters dont like to get hit, will want to take limited damage through the unholy proc (may also help pet out a little... enchants for pets, im a guiness) and flat out crusader for shamans.