My only thought is to wait and see. Give them a chance to shoot from the stems. If there's no sign of life by July they are probably goners. Have you scratched the bark to see it it's green underneath?

Splitting bark sounds like cold damage. I wouldn't wait around on replacing these with something hardier.

These lavenders are hardy to my zone and are 3 years old and have survived winters past. I'm thinking since this past winter was really bad with sub zero temps, it might have done something to them.
I did the scratch test, thanks Floral_UK, I totally forgot about that one. All 8 have different results in different spots. So I did the scratch test on the main stem of each. It's all good there. I'm wondering if its too soon to prune? They are really big sized Lavenders and it would be a shame if they got woody. I usually prune after the first flowering, but since there is a lot of dead and dry parts, would it be a bad idea to give a good prune?

I agreed. Wait and see - you've got nothing to loose. I must say that it has been a hard and long winter here in the Northeast. If your winter has been the same, definitely wait. New growth is still some while off so I would wait to prune the lavender. Do it when the temperature gets more mild and perennial plants start to show their new growth. That is the time when plants like sage, thyme, and lavender perk up and begin to show what is alive and what is dead.

FataMorgana