I believe there are more significant skills than alertness and healing, when you consider TB's justification.
I wholly agree with Ln about the healing skill. If I were to get a wish in the early stage of the game, I'd rather wish for gardening or herbalism than healing.
In the long term, the latter provides fewer benefits simply because herbs can be used on demand to restore large amounts of HP and you gain a source of toughness, willpower and dexterity training.
If I really needed regeneration, healing would once again be my secondary choice because of the clear superiority of items granting regeneration.
As for alertness, I guess I can agree with TB to some extent.
It is a nice and useful skill but after a number of games without it, my conclusion is similar to that regarding healing:
If I had a wish in the early-mid game, there are much better choices than alertness.
Furthermore, in the later game it doesn't really matter anymore, since HP pool covers you in this department.
The only place where alertness has a potentially game-changing effect is the ToEF.
PCs there often are under-equipped and having the wyrm miss you several times due to successful spell evasion granted by alertness, might just give you enough time to put it down.
This however assumes that the skill is developed, to somewhere around 80+.
That is very often not the case with wished-for alertness, simply because it levels up so poorly.
When you consider the above, healing and alertness aren't really out of the line when compared to other skills, especially when you factor in the frequently low starting dice that almost do not improve as the game progresses.
This difficulty in training further stunts the usefulness of these skills when wished for.
Hence, I vote to have both healing and alertness available via wishing.