So, when you play at harder difficulty level, your damage is lowered and enemies damage is improved. But does this affect let′s say for example, your summoned Dremora? If the damage doesn′t affect your summons, then it would most likely be the way to go in harder difficulty levels. Of course enemies still hit your summons as hard as they hit you, but was wondering how it affects your summoned creatures damage?

...And does your summons have HP so they can die, or will they perish when the spell duration wears off? I haven′t tried conjuration myself too much.

Good point. I'm pretty sure that the damage modifier does not affect your summons. The battle between your summons and your enemy is not affected at all by the difficult level.