I've had both of two extremes so far. The 1st ancient statue I killed got me a card, yet I've spent about 15% of my play time on the same character just grinding for a Worm card (totalling about 4 hours). Still don't even have it yet.
I'm still pretty sure most card drop rate posts are placebo. It's not like you get the same frequency of posts for the earlier areas of the game
[Edit]: Also, in relation to card dropping before mask, because the mask is an item, it's likely that it'll have a higher drop rate. I wouldn't say this poll is particularly good evidence for the card drop being low.
I should also really get around to that skewed drop rate formula