It's pretty easy to shift out of chilling cloud and not taking a penalty to attack, and vs. Will is often considered a benefit
Fair enough. We have a wizard using chilling cloud; and it's a double edged sword: shifing out often means not respecting a defenders mark, and, of course, there's not always space, you may need to give up your flanking position, you may be immobilized, etc. It works OK, anyhow; and a will-targeting power that's basically the same but without the -2 penalty would be less attractive.
Psychic lock can make the version in the article a lot better; but then, lasting+frost+wintertouched can help chilling cloud.
Granted, the power in the article looks better - but not by a huge amount. I'd say it's the enemies-only line which should go; without it, it's powerful, but situational (and quite comparable to the invoker power), as-is, it's too good.
I'm not a huge fan of damage becoming stat-mod-only fixes: the problem with these is that they slow down the game and contribute to grind. Particularly if the effect is mostly defensive (i.e. OA prevention and possible a -2 to attacks). The wizard that picked chilling cloud in our campaign, for instance, did so at first level. I wonder if he would do the same at 15th, say... A certain amount of base damage per hit isn't a bad idea (it also makes the minion/non-minion difference a little less extremely noticeable).
In any case, we don't need another chilling cloud - that power already exists ;-).