Almost all “normal” damage is and should be repaired online with zfs. Those offline repairs meant the hardware controller had no idea how to interact with filesystem directly, probably for the best. Level of abstraction purists don’t like this aspect of zfs.

If something particularly bad happened, or you tried being really “clever”, you can get into a rare situation of not being able to import the pool or have it import in read only mode. There are tools to help repair that kind of metadata damage. Then proceed with the normal online repair if needed.