To me this is more of a PrC concept... then again I feel Duskblades and Samurai should be PrCs as well.
One thing that puzzles me is how some of the martyr's abilities are supposed to work. I can understand healing for HP, but adding extra damage bonus to an ally? Of course this doesn't really have anything to do with mechanics, just something that people might find a bit strange.
A few things:
1) Martyr's attack adds the bonus to what? Damage? Bab? Both?
2) The damage recieved for Bloodletting is skewed. Save DCs don't nearly advance as quickly as the relative CR of that poison. A first level Martyr would be killed by this use from a relatively harmless poison (save DC 12), but a 5th level martyr could negate otherwise deadly 3d6 con damage poisons by only taking 20 damage. I'd look for a better way to scale the HP loss for this ability. Then again poisons are a joke anyway
3) Range of Life syphon?
4) Does Martyr's Stance have limited uses per day? If not this could be a bit too powerful, instant regen after each encounter?... at least for a cohort.
5) Martyr's power: again no range specified.
6) Martyr's Focus: Flavor wise this lends itself more to a Cha based DC, and make it 1/2 class level.
7) Divine Providence: It sounds like the weapon recieve both Lawful
and the chaotic Descriptor? Isn't that conflicting, since the character would have to be True Neutral or suffer two negative effects from handling a weapon opposed to his alignment.
7) Ultimate Sacrifice: is this an action? Which one? Does the Martyr need to maintin a focus or is this just an automatic ability, that he can turn on and off at will?
I can see some combinations that would make this class effective... sorta. Sanctuary with M. Stance or Ultimate Sacrifice for example, but overall it is underpowered and would not be very fun to play as a PC I imagine. I mean your character is there to get killed
... not fun. It would make for an interesting NPC class though.
I would give him good Will saves as well. He is a martyr after all... maybe immunities to fear and some mind-affecting conditions at a higher level. Actually I'd even give him immunities to poison/disease, just fits with the class.