I am encountering much the same issue, specifically with Druid Zookeeper characters. When these characters have their full army active (e.g. 1 vine, a few Ravens, 5 Spirit Wolves, 3 Dire Wolves, a Grizzly Bear and an Oak Sage spirit, when they encounter a large pack of hostile monsters, first the screen starts to blink in and out (it goes dark and then recomposites itself, a half second later); then eventually the screen freezes altogether and the game crashes.
This is VERY annoying and it makes this type of character all but unplayable. Interestingly, however, I have NEVER encountered this screen bug when playing a Necromancer – even one with a much larger army than the Druid’s one. So IMO it has to have something to do with how the D2R game code is handling the Druid’s summons as opposed to the Necro’s.
EDIT : Have confirmed that this bug very rarely, if ever, occurs during gameplay in “open” areas (e.g. Blood Moor, Cold Plains, etc.) in daylight. It seems to occur (and is easily reproducible) in darkened areas or enclosed areas (e.g. Pit, Catacombs, Sewers and so on).
By the way, this is on a W10 computer with a nVidia GT 1030 card (2 Gb VRAM) and a Intel i5-4570 CPU (16 Gb RAM). So it is way over the supposed “minimum” specs for this game.
EDIT : Should have mentioned that all video options have been turned way down (to “Low” wherever possible) and VRAM usage, per the built-in tools in the D2R client, show that only about half the VRAM is committed at the time of a crash.
EDIT : Experimented with removing the A1 Mercenary’s “Edge” bow to isolate the issue, but unfortunately, it recurs whether or not her Thorns aura (via the “Edge” Runeword) is benefiting the Druid’s summons.
EDIT : EDIT : Upgraded to version 32.0.15.6094 of the nVidia video device driver (for Windows 10). Testing is still ongoing, but it does seem to be less vulnerable to this kind of crash.
Please fix this stupid, crippling bug ASAP – it makes the game a bad joke.