Our raid was able to figure out the cause of client crashes on PTR currently. Everyone within combat log range of someone who is casting a CHANNELED SPELL that doesn’t have an EXPLICIT TARGET causes everyone to immediately crash.
Spells that does this include: Mage table, warlock summons, warlock soulstone, druid hurricane, hunter volley, druid tranquility. We have tested all of these and they crash everyone besides the caster 100% of the time. Every time.