I started out with 5 summoner witches, got em all to level 60 without too much issue, but around merciless docks I started noticing some serious lag issues with all their summons and auras up. I could play for a bit, but around once an hour, sometimes a couple of times in an hour, one of my boxes would freeze up and disconnect, or crash. It was annoying so I experimented with different settings, different auras, and finally less witches. :p I'm running maps now without much problem, but I don't run more than three at once because I don't really want to lose maps due to disconnects, or die due to lag.
I'm super excited that they've finally addressed this in the latest patch, I'll definitely be dusting off my two neglected, still-level-60 witches and taking them all out for a spin again. If all goes well they'll definitely be joining me in maps.
Setupwise, for people that are having trouble:
Absolutely make sure to have the exact same run speeds, this is the number one cause of headaches. :p Navigating some areas are a pain (I hate indoor maps
), but practice will help, and smooshing everyone into a corner now and then for a group hug is usually very helpful. Bind a key to toggle broadcasting to something easy, I use it *all* the time and it makes things so much better. Have pickup also bound to a key (in-game settings), and generally toggle off broadcasting when you're picking things up if you don't want the others to get all full of white crap. For a while I had it set up so only my "leader" would have keyless pickup, which works well, but is a huge pain if you want to switch leaders around, which I do often.
I run 2 auras per witch, so my minions get a shitton of boosts, without mana-starving my witches. I was originally going to have my witches be more support-based (was contemplating dual curse and dual totems, even necromatic aegis), but they were doing pretty good damage on their own so I've pimped them out and they're decently face-melty along with my minions. Their main skill is firestorm, just cuz it's nice AOE that you don't have to worry too much about aiming in a group. Any decent AOE or non-targeted spell will do, really. Just recently picked up Chaos Innoculation when I noticed that the only thing that'd been killing me in maps lately was chaos damage.
Gonna go test my 5 witches now, I'll report back how it goes.