I for one don't know what deleterious means but I have spent a lot of time peering around the insides of these heads. So far I have never come across something looking thinner on one chamber in areas, bent, having different sized holes, or looking worn out. It is my opinion, which has been developed by listening to the many fateful stories that I have heard about heads with un-clearable clogs, that these problems aren't lite switch type problems. What I mean by that is they don't reach 100% terminally clogged in a week. From what I understand many of these deadly clogs were first troublesome, but to a degree manageable. Until they were not anymore.
What I have actually seen while exploring the microscopic world inside these heads is that many chambers have hardened ink lodged inside of them, but at the bottom of the chamber, so at the top ink is still passable. While other chambers are completely clogged, floor to ceiling. If you keep this paragraph in mind, and now recall the one that preceded it, you might now consider that power cleanings (which are the cleanings that fire the piezos - which flex the sometimes unflexable ink-locked walls) are most dangerous when we need them the most. My bet is that a semi-clogged chamber will benefit greatly from a power cleaning, because the movement and heat will dislodge the semi-hardened ink and discharge it from the head. My other bet is that a fully clogged chamber, with it's chamber walls locked from moving while the piezos are firing, is the chamber that is doomed to permanently fail. I don't think there is a semi-fail, a close to fail, or an about to fail head. I think your head is failed, or not.
Definitely print between cleanings, like Mark says. And definitely do no more than, quick, somebody pick a number, (1?) power cleanings before you resort to plan... "D" - which is we don't know yet.
In my opinion you do pairs cleanings first. If that doesn't work you try them in serviceman mode, there are four different levels. If by then you still have your clogs, try power cleaning. But after one power cleaning if your clog is still there, maybe you've got a problem the machine itself cannot solve. Once those piezo's can't flex, your machine's hands are tied. But I really think it's too early to consider it dead. Maybe bury it, but tie a string to it's big toe with a bell on the end of it, just in case. In the mean time, I'll be on the graveyard shift.