I have it, and I like it. It's not necessary (then again, is anything ?), but it certainly helps.
Softcapped defenses or not, a few hits will get through every once in a while, and forts haven't too much HP ; using Aid Self often lowers the probability a bad luck streak will kill me.
I used it on my Widow from time to time but I think that was because I was always trying to see how much he could handle. I recently turned him into a fort to see how they played and although I would have wanted it while leveling up, I really don't need it at 50. When I get hit, I get hit hard and there's that moment of panic as you see how far the green bar goes down and you're like, "stop...stop...geez," and you're grabbing at a green insp. but it doesn't happen that often. I specced out of it mostly because when I really wanted it, I would get interrupted.
Get your hps up and your regen up as much as you can and that should be just fine.
IMHO I dont like aid self, its very situational. If you solo a lot you can pop it between mobs but then again you can rest between mobs. If your on a team chances are you'll have someone with some type of healing power, and for the amount of time you will need aid self you can just pop a couple greens and get the same result.
It all depends on your play style, and worst case you respec out or in to it later.
So I finally made my widow, soon to be fort (and I'll probably mess around with night widow some too with secondary build), and I've been trying to come up with a good build. So far from experimenting, I can get soft capped defenses with mind link up (lowest is aoe with ~47), but I can't perma mind link and hasten with the amount of money currently available (no money for luck of the gambler).
My question is, since I could easily find room for 2 powers to grab aid self, would you recommend it for just a general all-purpose PvE build? Or is it really overkill and totally not needed?