[Dion]

It really doesn't matter if the enemy can see you in a trench, because hardly anyone ever gets killed in a trench and most only receive suppression or become pinned, and being pinned in a trench is hardly any different than being non-pinned in a trench.

Also, units "heal" a lot of suppression when in a trench, and being pinned in a trench usually lasts only 1/2 a turn. Many times, I will fire at a unit in trench a hundred times, they receive suppression and become pinned as normal then they are returned back to an unsuppressed state in their half of the turn, so by the time it's my turn again their back to normal. You either have to wait for them to collect a lot of suppression and run after waiting for about half the game, assault them with high explosives, or use high caliber artillery.