Mission : Purge The Alien (Modified)

The Purge the Alien mission could be more balanced.

In the last Tyranid attack on the Eldar the mission was simple, 'Purge the alien'.
However; with 21 Tyranid units vs 11 Eldar this was very likely to be one sided
and would have ended as an Eldar victory 14-7 on primaries.
This did not reflect the game.

We played a modified version which scored the Eldar winning 15-14 on primaries.
This did reflect the game but involved a bit of admin to maintain.

I think we should play under the following modified rules :

Modified Purge The Alien
One Victory Point for each enemy unit that has been completely destroyed
(as per the standard mission)
PLUS
One Victory point for each unit from your primary army that has survived
(not completely destroyed).

EG
If the Tyranids had 20 Units vs 10 of the Eldar.
Eldar kill 10 Tyranids, Tyranids eat 5 Eldar units.
Final Score : Eldar 15 (Kills 10 + Survivors 5) vs Tyranids 15 (Kills 5 + Survivors 10)
Draw
as Both sides have killed 50% of the other.

I think this sounds fair.

What do you think ?