Wasn't a good winter for N.Z. flax here :-( Try pulling on some of the interior blades - if they resist well and the base of the plant in the interior is still firm and not mushy, then the roots are still viable. You may even see a few new shoots. Remove all the outer portions that may be rotten or mushy and cut the remaining foliage back to just above the shoots or to 4-6 inches. They're not gonna look like much for the rest of this season but they will eventually regain some form and stature. If in a very conspicuous location, you might just want to remove and replant.

If only a portion of the foliage is damaged - bent, spotted or with dried streaks in center - selectively remove those with the worst appearance.

This has been a tough winter on phormiums, that's for sure. Whether to cut the leaves to the ground or to selectively remove floppy ones is really up to you and your preference. Both will be fine ways to refresh your plant, so just go with what you think will look best.

Some of my phormiums are absolutely unscathed from this winter, and some have serious damage. On the promiment ones that have some damage but still have plenty of good foliage I'm thinning out the bent/damaged foliage. Others that are less conspicuous are getting cut to just above ground level. Definitely follow GG's tips on investigating your plants to make sure they're viable.

Let us know what you do and how it works out.
Take care,
Grant

I'm going to replace mine. I don't want to wait half of the summer to find out that it puts up a few struggling leaves. I might heel it in in a back corner and see what happens. Unfortunately, I really like it where it is (Sundowner I think is the variety) so it's not an excuse to try something else, I'll be rebuying the same thing.