Mortal and para blow for pvp. Armor ignore for pvm with mana leech weapon.
For sampire use area specials like momentum strike(bushido spell) and whirlwind on macing weapons for spawns. Double strike for solo monster killing is preferable with macing, fencing and certain swords weapons. Double axes are especially effective as well
Pretty much this...
As far as solo pvm: armor ignore for monsters with all high resists. Double strike with high dmg weapons is preferred when monster has at least one low resist.
Multiple target pvm: whirlwind or frenzied whirlwind unless you can kill the critters with 1-2 double strikes.
For pvm as mentioned it's best to have either hit mana leech weapons or use wraith form.
As for PvP pretty much mortal and parablow are the most useful. Bleed can be a nice disrupt, but you really want to be on a tactics mage to take the benefits of this. Some of the other specials are fun to mess with, but not necessarily effective. Disarming an archer is fun until they start chucking pots at you. Conc blow is kinda funny as well. If you just want to be a douch use any macing weapon and kill people's armor. Infectious strike isn't as effective as it used to be unfortunately.