Overnight (Sustained) 75% Drop in Traffic

Hey all, long story short I run two sites in the legal services area full time and the November core update hit us HARD. 75% decrease across both sites overnight, and despite all efforts, we haven't bounced back from the spike yet. (Updating core content, posting new high quality internally linked blogs, improved site performance) Is there anything actionable to do at this point outside of existing tried and true strategies? Does this point to a bigger core issue with our site?