Hi,
I did beat the Campaign using a summoner Build, I have to warn, Boss fights are brutal with this build, but it works. Had of course several tries to beat act2 and act3, learning the attack patterns, reworking the build, etc., act1 seemed pretty ok. Maybe pure luck.
The damage seems to fall of compared some builds I see on Youtube, but I saw people in general complain about mages being a little weak.
I guess Bossfights are brutal with any kind of mage, maybe I'm wrong.

What made this build work for me was combining the minions with Plagueburst and choose the option that poison stays behind when they die.
Also Livor Mortis has to be Mage or Melee, the tank did not work out for me. Living Swarm are mostly distraction and/or suicide bombers bringing poison to the enemy. I think changing there damage type to poison also made them more useful for me, but other options should be viable too. Also for hunting swarm changing damage type did help or when leveled up, choosing every single damage up point. So the ranged minions and the poison staying behind are my only damage sources, as I run aether jump except from those spells.

Parasite seems to be completely useless as I was never able to take over one single minion during boss fights. Not sure if that is a bug or intended, but in the end, I did not care and just quit using it. However, It was not too bad in the early levels against mobs (act 1).

I really want to second that the information how any stats from my character are transferred to minions is not quite clear, I too would be very interested.
But something must be transferred, otherwise I could not have beaten the campaign. Anyhow, with a little more information for how this works it would be possible to optimise a build a little better than with try and error as I had to do and I am sure my build is far from optimised.

AI seemed to work mostly for me, probably not perfect, but not horrible either. Yes they wait for monsters to revive, but pretty much delete it afterwards instantly, so it never was a problem for me. Most of the smaller mobs are pretty much deleted by the minions now, leaving the poison for the elites.I think the Caballist Primordal Insights passive for instance did work with those clouds making it not too shabby.
Hope that helps to get you some fun using a summoner build,
Sorry in case I am describing something bad or got something not quite right, I have not half of your hours in the game and it is my only character, so I have no real comparison to other builds.
To wolcen: Nice Game so far, I like it, But yeah needs some polish here and there but seems as you are working on it. As mentioned, some info how stats for minions work would be interesting.

Cheers

IN the act 2 boss fight, the minions dont atk the boss, they just stay frozed lol, and the AI of the possessed ones are rly bad, they stay behind you alll the time, you have to drag the enemys to hes feet so he can start atk. and like you said.. they have poor dmg and poor life. rly bad times for summoners. i hope they improve it

Minion AI definitely needs some work. Overall they need to be more agressive than they are right now. A boost to their movement speed would be welcome because they don't have gap closing skills (with the exception of Livor Mortis with the shadow modifier).

Their health and damage is pathetic at best. The trio of PST talents that sacrifices your character's health and force shield in exchange for damage reduction on the Minions should make them all but unkillable. It's far from that.

To the devs : please clarify how minion damage scales. I know for taking a look in the game files that they have a base damage value that rises with their level and that each Minion type has a damage multiplier. But what about our own stats ? Do they inherit any of it ? If not, you should definitely make plans to change that. Minino damage scaling is a must. There's a reason why Baron Zombies are so damn powerful in PoE compared to other minion builds.