Minion Witch can't tank

The best defence is the offence.
The core thing here is too buff yuor minions damage and use such sup gems that everyone dies before reaching you.

Id reccomed to watch some youtube guids if you are feeling something is really wrong and you cant normaly proceed with clearing.

Even without insane meta Ants this league, usual Sceletal Archers can do decent job in t15. The main thing is to get +lvl to minions whenever you can, its your main source of success.

+4 on scepeter
+2 on focus
+2 on helmet
+2 on amulet
+ on sup gem.

And you got lvl 30 guys (19+11). White mobs wont touch you.
You can get more but at a heavy price.

The second main source is + Spirit.

This all above may sound obviuos but there may be some item types\suffexes\gems etc you just didnt see and dont know they exist.

For example Bones of Ullr boots that give you - Undead Minions have 20% reduced Reservation -
Or Abyss reservation spirit desecrations for armour and helmet.

I second the above post. I've mained minions since release and you just have to juice them up.

I would suggest archers and getting + minion skills on your helm, amulet and scepter.

You'll want every damage node on the tree and cap all resist with the exception of Chaos (I've never done mine past 68%)

Archers are good because they always get first hit and normally second hit before the mob is in range to do anything. At endgame with at least level 28-30 minions (from + to minion modifiers) they should be 1 or 2 shotting most things. You can slot fork for help AoE clearing.

Stack spirit and get one of those timeless jewels that lets you gain +12 spirit from each of the the keystones you pick inside the circle. Then just keep adding archers. When you can do the 3rd interlude, get one of those ants from the ashen forest (there's only 1 per map run) as a specter and try to get to where you can run at least 2 or 3 plus archers. For clear, use detonate dead with raging spirits plus the archers. Works like a charm. i just hit 96. Lich seems superior for the chaos damage aura, life cant be moved while you have energy shield (so you can constantly use pain offering to buff minion damage), and the jewel slot ascendancy that doubles the effect of a good minion jewel.

Good luck.