If the shot in the rear hull is redirected fully on the side hull, does the player still get the token?

Can you post the wording from the card - don't have mine to hand to check.

Yes, because the attack was made against the rear hull, and the defender suffered damage (the card is non-specific) - it doesnt say "If the defender suffered at least 1 damage on the rear hull zone"

Redirect seems more theamatically to represent drawing shield power from another facing to reinforce the facing that is being hit, so the hit isnt going on the side, its the ship is drawing power from the side shield to reinforce the back shield being hit.

"After a ship or squadron performs an attack against the rear hull zone of another ship, if the defender suffered at least 1 damage, the attacker's owner gains 1 victory token."

I will admit on first reading of the card though I thought it only meant if the defender had been dealt a damage card - rather than suffer any damage - i.e. hitting a debris field is "suffer 2 damage" but that can be on shields, so it just means actually causing a hit.

This makes this potentially a very powerful objective for the rebels then against Victory Star Destroyers.

The defending hull zone is still the rear hull. You are merely redirecting some damage to another shield. Or as I prefer to imagine it, redirect some shield power from the side to the rear to catch those shots.

What they said ^^^

This makes this potentially a very powerful objective for the rebels then against Victory Star Destroyers.

Yes it is, especially if an X-Wing manage to bypass the Tie screening.