Excellent idea, only a few things need to be fixed:
If i cast shrink on a wounded unit it will heal the unit and hurt it again.
The end of the spell effect is also buggy, sometimes it doesn't even recovers from the effect (so it remains small), but sometimes the effect ends immediately.
I've looked into ur triggers, so i know the source of the problems:
first, it sets the life of the target unit always to the x% of the orginal life instead of hurting him.
I think you should make the following action:
Unit - set life: current life - 0.1x max life
(that will decrease the unit's life with 10% of max life)
the other problem is caused by a variable: for example i cast shrink on a unit:the trigger sets the ShrinkTargetedUnit to the target unit, then shrinks the ShrinkTargetedUnit. Then i cast shrink on another unit, the trigger sets the ShrinkTunit to the unit i targeted now. After the first shrink's duration is over, the trigger will unshrink only the second unit, coz the variable has been changed.
Can be easily fixed: set the cooldown of the shrink spell to 25 seconds. Then people won't be able to shrink multiple units.
If you can fix these bugs itwill be a really great spell. The idea is really excellent, there's only 1 thing i could add: the shrinked unit's speed could be also reduced... (but this doesn't matters)
Anyway i'm so unlucky... I acidentaly always find the all the bugs of a game..
