Just a tad confused here. Say 4 of my troops in a unit can see only one troop from another unit. But one of my troopers can see all 5 of the defending unit. Can I potentially inflict 3 wounds on the enemy unit should I roll the required dice?

If at least 1 mini in the attacking unit has line of sight to a defending mini, that mini can be assigned wounds. So in your case, as 1 of your minis has line of sight to the 5 minis of the defending unit, you deal 3 wounds, killing 3 of them.

Thanks for that. Seems counter instinctive