The life span of an atronach is mostly dependent on which one it is. Frost ones can take a fair bit of punishment, they've even got a 10% damage reflection going for them.
Flame ones are mostly good as distractions, when you're low on health and magic and you need something that will take the heat off you, pop one off and the enemies usually spend a good five or ten seconds chasing the thing down.
Storms have the best dps of the atronachs, combined with a potent Shock cloak and decent speed and health. I use Storms to fight dragons in outdoor areas, because they somehow manage to score hits on the thing when it flies around, and they tend to move away from me. That makes them good distractions, the dragon cooks one of them instead of me, because I'm in cover.
My biggest complaint with zombies is that there's never a body around at the beginning of a fight, and I really hate being the center of attention. I'm a glass cannon mage, my use of Morokei nerfs my armor by negating the Mage Armor perk in favor of more magic for my crazed lightning spewing. 150 health+ minimal armor+ lvl 40 or higher enemies= don't get hit. I knew that when I set up my character though.
These sorts of arguments are tricky for me because there's so many ways to play this game that will work. I'm sure your way does get you where you need to be, and it's not like my build has never gotten me killed. I just prefer the versatility allowed by being able to summon something without having line of sight on a body, and the power of the spell being limited to the quality of bodies around you.
By the way, what's your opinion on the Dremora Lord? I found them to be extremely powerful allies, even though I couldn't Chain Lightning with them active.
