Average destruction is all you need as a tiebreaker. Average destruction of all possible attacks (taken and not taken = 2x number of players in war), and not the average destruction of enemy bases. The average destruction as currently implemented is completely redundant, since a perfect war guarantees 100% average destruction to both teams.
Yes, the second attack becomes important now, and you can't simply rush the opposing #1's TC for 2 stars (and max loot). You will have to pile on the bottom guys to guarantee maximum average destruction, and again this will be great against sandbagging alliances, since 100 percenting the bottom guys will be easier.
Loot gained in war should be secondary anyway to improving alliance reputation (call it glory, XP, medals, whatever).