It concerns me that you didn't even look at the spec before replying, but I guess that is your prerogative. Had you looked at it you would see that I do in fact keep the 2% healing received.
I did actually look at it, but it was late and I missed the Shadow Shelter talent (sorry!). In previous discussions, this talent had been dropped.
Even with the 2% healing received, you're still requiring almost 11% more external healing. As I said in my post, this is a really bad trade. You're mathematically MUCH better off switching to all B mods (which you can get for coms) and a few Fortitude augments. Endurance stacking fixes the spikiness issue outright at the cost of significantly more healing (but no where near as much more as this hybrid spec requires). It's not a *good* solution, but it's better than sacrificing Wither for a mere 25% DR cooldown.
Obviously the point of the spec is not to use this new cooldown with some type of unattainable clairvoyance. However, the problem I am running into is getting hit with a series of unlucky/unmitigated attacks during which time I (a) have no cooldowns available, and (b) cannot receive heals in time before I die. This spec adds 1 more cooldown to use in those situations, it basically buys 6 seconds to get some big heals cooking on me.
Generally speaking, I rarely find myself in a situation where I've been spiked hard and I *don't* have a CD available. The problem is more that I get spiked to DEATH before I have a chance to react, and the spikes themselves can come in rapid chains (sometimes unhealably fast). Having another 25% DR CD is nice, but it doesn't address that issue.
Like I said in the original post, the reason sin/shadow tanks are failing is because of the burst. If I increase the heals I need in the aggregate by 5-10% at the cost of not dying during a boss pull then I count that as winning. Let's face it, healing in this game is more than capable of taking up the long term incoming damage this spec creates; and the spec prevents the short term damage from causing a wipe.
Sure, but what if you could increase the healing you need by just 3-5% while addressing the spikiness issues in a way that *actually* works in all circumstances (i.e. not requiring manual intervention)? Wouldn't that be a better deal? You get that if you stack B mods and a few Fort augments.
Baring a real fix to the sin/shadow tanking tree/kit I will be playing this spec to clear NiM content as it is the only way I feel safe handling the massive burst damage that we are seeing.
I wouldn't. NiM Dread Guard is still primarily an efficiency fight. The primary bit of spikiness is in the third phase with Kel'sara's Discharge paired with Clairvoyant Strike. This spike comes once every 30-45 seconds with a probability of just 10% (still unacceptably likely, but not a consistent thing). I have found that I always have a CD up for when this spike happens.
Your build will require 11% more external healing, which translates into 165 more HPS. That doesn't sound like a lot, but when the healers are already essentially at the extreme limit of what their energy regen can support, every bit counts. You might be able to clear the boss with this build, but trust me when I say that you're going to make your healers work a lot harder than they need to.