I am not saying minion damage is great, but I deal more damage with minions at lvl 81 (running tier 41 NM dungions at the moment).
I agree that Warriors hit like wet noodle, at the moment their value is in making corpses (reapers) and taking hits instead of you.
Mages - blizzard scales with your damage not with minion damage. In general you want to stack total damage (int, +damage%) because it affects your minions too, minion damage bonuses, vulnerable damage because it is multiplicative with overall damage and any kind of % damage from legendaries and skills because these are multiplicative too.
Especially unique peragon node from cult leader, golem board, corpse eater, hellbent commander, passive bonuses to minions from skill tree. Some of them might not show up in your stat sheet but they work. It is crucial to take Shadowblight key passive instead of Kalans Edict (which does not work most of the time due to damage taken anyway). Once you have Shadowblight you can use most powerfull minion buff available to necromancer - Blighted aspect, which is available from dungeon but can roll up to +120% bonus damage to all damage done including minion damage once your blight ticks 10 times (+240% bonus damage on 2H weapon!). Best way to get ticks of this quickly is bonestrom with the shadow damage aspect, miasma corpse explosion, and blight. As mentioned above this is multiplicative bonus. On top of it you can combine it with inner calm (up to 30% damage when standing still) and conceit (up to 25% bonus damage with barrier on, you need barrier aspect for bonestorm too).
Golem - doess OKish damage with auto attacks, but its main purpose is to bash with the active (either blood or iron golem) with blood golem you can deal huge damage if you have the 50% bonus damage when healthy for the golem and you hit single target such as boss, though most usefull one is iron golem because it has only 10 second CD, does better AOE damage than blood golem (15 sec CD), stuns and can apply vulnerable.
Now other very important detail is decrepify, and crippling darkness passive, both of these can proc stuns, so you can jump into middle of enemy group with bonestorm, proc some stuns, stun enemies with your golem and freeze them with your mages while you are effectively immortal (due to barrier from your bonestrom).
Last but not least, decrepify can also proc CD reduction, so if you already have bit of CD reduction and got the 3 legendaries for bonestorm you can have almost 100% uptime with it, and your golem can bash (and stun and proc vulnerable) almost constantly. Finally you want to have oh shit button in the form of blood mist (which can also produce corpses for summons, bonestrom duration increase and it can tick CD reduction from decrepify aswell).
At least thats how I play late game and it is working so far.
However I agree that minions (and some other builds like blood) should be buffed or bone should be nerfed. Especially bonus damage on warriors is absolute waste due to their abysmal base damage.