Can a resynchronization be avoided when recovering a wallet in Bitcoin Core?
The only way to avoid a full resync is to make sure your backup contains the blockchain as it was when you made the backup; not just your wallet.  

Then the core should only need to update with any more recent transactions.

Here is a good article on the subject:  http://bitzuma.com/posts/moving-the-bitcoin-core-data-directory/

And here it is from the Wiki:  https://en.bitcoin.it/wiki/Data_directory