You see, anything pre Ulduar doesn´t benefit from logs at all, they are completely meaningless because the content is simply too easy. So no, healers will not contribute in any meaningful way if they deal damage.
I remember in Wrath, I would only start doing damage at some stage mid Ulduar, when every little bit extra did help. Hard modes, that is it, not even normal Ulduar benefits from it.
Bring one or two less healers: that way you gain real extra damage and your healers will be busy. There is absolutely no need for 6 healers in Naxx25, but it is normal to bring them at first. Soon enough we will see guilds clearing it with 4 at most (A holy pala, a disc and 2 AoE healers).
Logs in classic are like gear score, laughable
They can be used for fun.. but they are not more useful than the details addon.