Will/DA... Thoughts, but mostly questions

The Whispering Man is a Willpower/Dark Melee Tanker... like most of my characters he is concept oriented, sort of a Shadow/Sandman (original guy in gas mask, not Gaiman era) guy. He had originally been Dark/Dark but the swirly misty things kept obscuring his outfit... I switched him over to Willpower and found that the Dark Willpower effects are nice and gloomy without actually obscuring anything.

Ever since i19, with the Stamina pool out of the way, I've discovered that the mid-teens were a breeze for the guy (teens have always been a pain in the butt for my tanks). And it seems to me that WP is synergizing really well with the dark set. Siphon Life seems especially well suited for a defensive set that doesn't have a toggle heal, and while the DM attacks always seemed kind of end-heavy that pretty much disappeared with Quick Recovery and Stamina, and will probably be negligible when I get to the point that I'm putting the fancy invention sets in.

So what I'm trying to figure out is, what guidelines should I use when developing this guy? I'm not asking for a specific end-game slotting map because he just hit 22 -- it's going to take a while to get there and I want him as effective as possible throughout.

First question: Siphon Life -- slot for accuracy and heal, damage secondary, or slot for accuracy and damage, heal secondary? It's one of the highest damage attacks in the set, and it's not DoT, so there's a strong argument (in my mind) for emphasizing the damage part... but... it is a heal, and I can see the tactical advantage in being able to get a bigger boost of healing when it's needed.

Second question: Defense soft cap -- any point in trying to reach it in a WP tank? WP does have some defense, but it's primary mitigation seems to be healing, and it's total defense for smashing and lethal isn't really all that high. I know there are inventions that can boost defense overall, though I'm not really familiar with them, and I don't know how much I'd have to sacrifice in order to meet that cap.

Third question: Rise to the challenge -- the description says it applies a to hit debuff for every person in range, but it's not very big (3%). Is this like Invincible (i.e., it stacks per target?) I haven't noticed any benefit from this at all, but it's slottable. Is there any reason to slot to hit debuffs in this power?

Those are all my questions for now. Thanks.

Siphon Life is a great attack, and should be slotted as such. You could, however, use a couple of the accurate heal sets in a frankenslot on the attack.

A softcapped Willpower is a fearsome thing. Now, that being said, you might consider softcapping against Energy and Negative only, as you do have the dual layers of resistance and healing to preserve you from smashing and lethal. On the other hand, building in even a moderate amount of defense would be beneficial, as you'll be stacking on the to-hit debuffs from Dark Melee. It's really your call.

Rise to the Challenge's to-hit debuff is not worth slotting. If you're interested in to-hit debuffs, look instead to Touch of Fear.

Touch of fear is single-target, yes? So how effective is it against the targets you'd really want to use it on, like Elites, AVs, etc.? I assume it won't do a whole lot to an AV. When would I want to use it?