This is literal bull crap. The lags and disconnects have existed the whole expansion and are NOT only in the raid. They happen open world, in M+, all over the place. Game servers are stuck like they are waiting on DBs to respond with acks. get your crap together please, many are so sick of it ready to unsubscribe.
60 seconds of searching turns up all kinds of people asking for you to pay attention and help for MONTHS:
Game freezing from ‘whole guild log in’ spam - Community / General Discussion - World of Warcraft Forums