Was having a discussion about our EoF AA spec with a guildmate assassin, and we started talking about Excessive Bleeding.
Personally I think it provides much more "effective" DPS than Repeated Stabbing (Frontload I have yet to look into) even if it doesn't show up on the parse.
Erkekjetter, however, raised the issue that it only says "max hitpoints" in the description. So, we (he) decided to take a look into it.
From both duals and fighting identical mobs it would seem that Excessive Bleeding works as follows:
Reduces Max HP of target by 1%
Reduces current HP of target by 1% of current HP
In duals Erkekjetter melee'd me down to about 50% hp, and then stopped and used Mark on me, I compared my HP before mark and after mark.
I have 5800 ish hp.
My max hp went down by approx 300 (5% of max) (I'm considered a weak target

)
My current hp went down by approx 150 (5% of current, 2.5% of max)
When the skill was canceled I regained both the hp and the max hitpoints.
We need to test whether the hp you regain is equal to 5% of your new hp (when damage dealt from other sources is considered) or simply regains an absolute amount of health equal to that which it lost on application of the bleeding skill.
Another issue raised was that in the past hp debuffs had a very detrimental effect when they wore off, a mob would actually gain considerable amounts of hit points, over and above what it lost when the debuff was applied. If someone could confirm or deny this I would be grateful
It is probably the case that for lesser geared, run of the mill, assassins Excessive Bleeding is the best choice, while if you sport a lot in the way of recast time reducing gear and buffs it would be best to go with Repeated Stabbing to allow for faster spamming. However I just thought we should clear up the whole excessive bleeding question.
It does work.
It does reduce current hp.
It does cause mobs to regain hp when it wears off, however the %age health the mob has will always remain the same, on application and removal.
Against the EoF mobs (lots of single target very high hp mobs) this skill really shines, with a 2% constant decrease on a mob with 4-5-6 million hp you are doing anywhere from 40k "effective" damage with each maintainable dot to 60k "effective" damage with each maintainable dot.
Ok, fine, it is not real damage per say, but 2 dots can be kept up ad infinitum, and those two dots effectively do a manaburn on the first time they are applied. You may not see it, you may not get a pat on the back for it, but it has reduced the mobs hp by that much.