On a PvE aspect, I think the skill is just lackluster compared to it's comparables: Mercy Stroke is simply flat out better for the use. I think if Soul Survivor was more in line with that, it would be a neater skill, but then you would have people screaming about homogenization and seriously, I'd be one of them too. I like differences between my classes. My only argument is that the skill itself is kinda boring. That's all. It's a fire, forget, and hope the thing dies within 15 seconds. I'm sure it has its uses but it just flat out isn't really required to be used. But on that note, so is Mercy Stroke.
On a PvP aspect, I can't honestly see the justification to ever use it because of the nature of the fight. And I don't think it ever was meant for a PvP use, really. You spike down people to get them to die before the healers realize who's being targeted. You can't honestly have enough clairvoyance to know when to fire it and have it ACTUALLY fire off with a kill. So yeah, I don't PvP but I could definitely see the uselessness.
Maybe they should just make it a 20% and below attack which is on a 15 second CD. That way, you feel like you can fire it and it'll do something...
Something of a caveat as to why exactly Soul Survivor is not the greatest of skills for me: I normally run with a SMN and BLM as my DPS in my runs, and a WHM healer. As such, there's a lot of AoE and the unpredictability of blowing SoSu on an add is difficult at best. I actually have to try to figure out at around 20% who to choose and at that point, with the amount I pull (I can normally pull 3 groups with ease but I have to pay attention to AoE because with Ranged as my DPS, direction doesn't necessarily matter anymore.) it distracts me from doing my job if I have to guess. So at that point, I actually forget the skill period. But with that in mind, I normally finish my fights with above 60% Mana so I can walk to the next group and have enough to do my opening.
Which leads me to my opening on these groups: I use a very mana intensive rotation to open up in order for my casters to go balls to the walls when attacking. And even then, I sometimes lose on aggro because of having so much chaos going or if I get unlucky with a tick or a hit or if my WHM wife decides to Holy too early while Blood Price is up.
Gather everything together, and by this point, I've already used Unleashed and Plunge as well as Scourge on some adds to keep them on me. At this point, this means I'm not at 100% mana. Drop Bubble, Unleash a couple of times, DAAS to get health/aggro, and DADP to blind them. That's a REALLY intensive amount of mana. We're talking at least around 80%+ of my mana at full bar. This is why I actually try to finish fights beyond 60% of my mana in order to make things smooth. And that honestly removes the absolute need of using SoSu.
It really depends on your playstyle. If you do it right, SoSu is pointless. Because, I have other things to do than to fire something that is somewhat meh. And yet, I still can fire off Mercy Stroke from time to time. It's because it's a one time shot that has DPS increase skills and allows me to kill something faster.
SoSu does nothing but when it dies. maybe if it had a damage DoT component..? That's all I can think of that would help.
Oh! Why not make it a 15 second cast, but a DoT drain? Every tick gives you a certain amount of mana/health! This would probably kill off the whole need of the burst at the end but I think it would be neat if it's some sort of DoT you apply to a mob that does a drain of sorts. If you want to keep it as something of a final attack, you could make it 20% only activated but I think that would be a neater way of dealing with that attack and keep it in line with Dark Knights.
Thoughts?