If the goal is to go through the campaign with zero losses of valuable units without saveloading, smoke in combination with cannon fodder is the only way I found, allowing to control where aliens will shoot. And melee weapons still can kill you in smoke. You need to know all of the alien spawn points as well so that Sheevars don't run to you and kill your Colonel with their plasma blade.
It feels like hard cheating to me that aliens have (most of the time) the better equipment, know from where they can see/shoot me before they start their turn (wow, what could I do with that), have much better starting positions most of the time, do not need to protect a bunch of wildly running around weaklings, can live with the fact that whether reaction fire will work depends basically on chance only due to engine buggyness as they don't need their units to survive, have better physical stats (hitpoints or resistances for sure, and I think also chance to hit), can be in greater numbers frequently (for base attacks and bombers is seems kinda unlimited), ...
Some cheats in the opposite direction are fine, such as shooting through walls or over them for instance. What, aliens can't do that ?
All of that adds to the fact that damage in 2.6 is so ridiculous that any single shot is instadeath, armor does not even protect from stray shots anymore and there's the well known suffocation from smoke, being a problem for any unit without nanocomposite armor.
So those who think that smoke is overpowered, may I ask you to provide a screen video or the like, showing how you play your missions without loosing valuable units ?