You can try popping smoke grenades on enemy ranged units so they're forced to use a turn exiting instead of shooting you. Bonus points if you surrounded them in fire first.
Also, if you hold "ctrl" you can shoot behind the cloud, but your hits will pass through hitting enemies inside.
A few suggestions for your melee problems:
Look into the skill Phoenix Dive, sold by the Warfare Lizard in the elf cave. It will be sold once your party is level 4. It grants the user temporary immunity to fire.
There is also a scoundrel skill that causes your character to float over ground effects, avoiding damage.
During the story, all characters will have an opportunity to learn Bless, which converts negative ground effects to positive ones.
You could also have your melee swap weapons temporarily to something ranged, (1 AP to swap a weapon in combat) or you could put a point into another skill skill with a few ranged abilities. For example, a point in Aerothurge could allow you to purchase Teleport and you could have your melee character pull an enemy to his location.
Generally zombies will release poison, and from any attack that would cause them to bleed, which is mostly any source of physical damage.
Edit: Didn't realize this was for DOS1 and wrote my response for DOS2
Last edited by error3; 12/12/16 03:26 AM.