-Enemies LOVE attacking your summons. They will frequently run past your characters to hit their summons.
-Enemies (on Normal) seem to prefer NOT to focus-fire your characters. If one character is near death, they seem to slightly prefer attacking other characters
-They don't seem to discriminate between your different characters based on how armored you are, or whether you're a caster.
-They do seem to like attacking the nearest target
-They do seem to prefer attacking what they can see, rather than running forward until they can see more (this can be used to bottleneck them in doorways).
The only mechanic in the game I've noticed that directly affects aggro is the 'Stench' talent.
