I am in the same boat with 2 tamarinds. I can't tell if they just defoliated, or the damage was worse. I guess I will just wait and see since its pretty springlike now.

I have a guava, but its a greenhouse dweller. I read on the Pine Island Nursery site that most guava varieties can go to the mid to high 20's without sustaining damage that would kill them outright.

I planted a mango outside last season as an experiment, it bit the dust at 22F

By guava, are you referring to the tropical guava (Psidium guajava)? I seem to have successfully overwintered my tropical guava inside my garage (on the coldest days, maximum temps were in the 40's and minimums were in the upper 30's). That seems cold for a tropical guava, but they look good and are ready to take off with the warmer weather. If they are really brittle, that does not sound good. There should be some green when you scrape into the bark. Good luck!

So they will normally drop all their leaves? and now should there be any pruning back required? If I find dead branches, should they be removed...I'm just wondering if I cut it way back or at least back to where I see some green in the stems/branches (in hope the roots are still alive) will it grow back?

And when should it be brought back into the sunlight? I do have GH now...so I could put them in there...but will they need any adjustment period? they've been in the dark...on occasion, I would open up the shed to let the air circulate, and I watered periodically too.

Well, my guava is in full leaf under the conditions I described. No, it is not "normal" for them to loose all their leaves but they can recover from this stress. My plant is in a garage but it is NOT dark. The plants have been getting direct south light through two double rows of garage windows. Still, I have previously overwintered guavas that did in fact loose all their leaves and these plants came back once warmer temps returned. I would cut off anything brittle and dead but leave branches that that had green beneath the surface when scratched. Start moving into good sun, hold off on watering (unless really dry) until you see signs of growth. In your zone, you should be able to put the guava outside some time in April. Usually mid to late April is safe where I am.

I have tropical white and tropical pink guavas outside. One is in a protected location and the other is out in the open. The one against a south-facing wall went undamaged all winter and even pushed new growth throughout the winter. The one out in the open lost about 50% of the leaves (mostly tender new growth). despite losing their leaves, they are not decidious, mine dropped damaged leaves. I would let your guava be. Don't prune since you might take off live wood.

Yeah, WAIT to prune until at least after April 1st. Zone 8 you still have a chance for a freeze...this Saturday here its supposed to drop to 33F.

Even though they are not really deciduous, a lot of fruit trees will defoliate in a freeze and leaf back out later after it gets warm. Some of my citrus do it.

If you prune now, you are sending the tree a signal to grow. Pruning releases a plant hormone that prompts new growth. Since you really aren't out of the woods for potential frost/freeze yet, wait and prune at the same time you plan to fertilize for the first time. Then just tip prune, starting at the very tips of the branches and cutting back inch by inch only til you get into live wood

Frost can kill Guava, even if you put a frost blanket on them the leaves will fall off, if the temps go below 32F around the roots the plant will die and never come back. We grow a few thousand Guava plants about 30 different Vars and we put them in a green house even in Tampa Florida. You can have 2 plants side by side but one will die from the frost the other will just loose its leaves. If it goes below freezing and you did not protect it, then its dead. You can scrape a little of the bark off the tree near the base, if the cambium is still green its alive, if not then pull it out.

Here is a link that might be useful: Nipa Hut Gardens and Gifts