Oppressive Gloom

I'm asking about the scrapper version specifically, but feel free to add the details for other ATs too.

Assuming that I'm at the target cap, how much damage is it doing to me per second?

Assuming I have the base value for max HP (ie, no +HP powers, accolades or bonuses), how much Regen is needed to offset it? A couple small bonuses, a Regenerative Tissue Proc, more?

Assuming I have capped HP, how much regen is needed to offset it?

I've been told that, on a softcapped DA, OG deals more damage to you than it prevents. On a Broadsword/Dark with about 15-20% def to all (before Parry), will that still be the case?

When paired with Broadsword, what are the pros and cons of taking Cloak of Fear over OG?

According to city of data, at level 50 it's doing 6.26 damage to you per tick per enemy, so a total of 31.3 damage/s when saturated (max targets 10).

Base scrapper regen is 5.58 hp/s, so 31.3 hp/s is 5.6 times your usual regeneration. So you'd need a total of +460% regen to counteract that, if I did my math correctly. At the HP cap your base regen jumps to 10.04 hp/s, so you'd only need a total of +212% regen, again assuming I did my math right.

Honestly, though, I wouldn't worry about OG's self damage versus regen too much - I have a feeling that incoming damage from enemies and healing from dark regen will be the dominant effects on your health bar in the long run.

To figure out of OG does more damage than it prevents, you'll need to know how much damage those minions would be doing to you, which is going to vary a lot. Basically, though, what you need to do is figure out a single minion's damage output per second, modify it by your resistances and defense, and compare that to OG's 6.26 damage dealt to you every 2 seconds. Note that OG will still damage you even if the target is an LT or boss which it can't mez, so even if a simple calculation says that the minion would deal more damage to you than OG, if the spawn is only half minions OG might still come out worse if it's on the border.

The -self damage isn't that big of an issue if you use dark regeneration or some kind of healing to back it up when you need to. I've only noticed its effect when I set it on x6 or higher and I run into the mob and I am not killing fast enough.

I use mostly on my Necro/Pain MM. Mastermind's version has 12' radius which is larger than Scrapper's.

On the topic of OG's stun-wandering problem, the Razzle Dazzle: Chance for Immobilize proc can help to mitigate this somewhat, but in my experience doesn't really do a very good job. It's a 20% chance, which is not bad for a proc but not really enough to keep most of the baddies in place.

Given a choice, I'll choose OG over CoF nearly every time. IF you can get to the soft cap then OG isn't as necessary, but considering Dark Armor has no DDR, OG can still be useful when you are de-buffed. It's also nice to have when you're at levels lower then your Soft-capped set bonuses are kicking in at.