afaik Mobster only spawn one at a time at seals unless something has changed in my time away.
It would take far too long to hunt for my tastes. Assaulter is kind of an okay replacement too (only 10% crit damage, but 3% more crit rate over Mobster in PvP / vs demi-human)
Paper is on my list.
I'm just going bare bones right now for the rate;
2 skellies for 18 crit (leaving room for 1 The Paper Card), 12 crit from brooches, and the remaining 20 from 60 total LUK which also helps with the curse-self effect from the brooches.
I'll eventually swap brooches for Rings with Goblin cards for the extra STR bonus and no annoying self cursing, but brooches are super easy to get once you have enought crit to kill Teddy Bears as they're way too hard to hit without massive DEX/HIT.