Some more thoughts on summoners-I didnt notice any relic options(pardon me, if I missed them). For my necro summoner I use the following relics:
1st and most important relic is Champions of the Sun relic. It allows you to summon 18 (in my case) melee minions, with 130-150 k life. They give the unbelievable 17% Phys res&47% elemental res. It is an aura, which affects you&your minions. Even if you have your res maxed it is very strong defense buff for your minions.
2nd relic is Dark Power relic, only in case you don't use the summoner set (Satanic mantra, it has it when you wear all pieces). If you use Lazarus set, crafted gear or sacred uniques it is big damage buff for the minions. 10% crushing blow+28% increased phys damage+300-350 magic damage to weapons. Now multiply it by 9 skeleton, 1 or 2x VK, 18 champions of the sun and 6xAbyss Knights+any other minions you might have.
3th relic is debatable, it is either Glowing Fungus relic or teleport relic. The choice is more damage(Fungus) or more mobility. In case you killed Innarius in the Void you have acces to teleport from his charm, so Fungus is the way to go. Funguses tend to die a lot, but they have very nice AOE dmg.Teleport gives you mobility and will save you many deaths, also I use it as Focused strike-you teleport upon an enemy and 1st strikes of your entire army land on the nearest mob. Teleport replaces Bend the Shadow thanks to the fact it can be used through walls/obstacles.