No I wouldn't put mulch over the crowns for winter. If you have very young and small plants you can find some branches from a conifer (your Christmas Tree? or your neighbors) and place them over the plant AFTER the ground has frozen. Remove these in later March early April.

Steve

Nature will put leaves and debris over crowns, and they will survive well. So I mow leaves over it to give it a finer texture making it more difficult for slugs to hide under. In areas close to the house I will distribute available bought mulches over all plantings including hostas. But I have a large H.'Blue Umbrellas' with the crown somewhat above the ground, exposed by winter rains, and it survives winter nicely.
I lost hostas due to crown rot over winter, but they were located in low spots with water collecting above them.
Bernd

If you could see the tons of tree leaves on my hostas right now,you would wonder how they survive,but they do every year,and I don't do anything until spring as far as removing any of them. In fact,you can hardly tell there is a hosta garden out there right now! Everyone to their own ways,but this is what I do. Phil

depends what the mulch is...

if it were fine leaf mulch.. ground up in the lawnmower until no bigger than your finger nail ... and it were the right kind of leaves [another reason to hate maples] ... it can be done.. AFTER GROUND FREEZE...

short answer.. you did good enough.. go find something else to do

ken