Confirmed, thanks. Monster aggro and jumping run on the server, and that part isn't done yet. The game side can already draw a monster's jump; the server half (jump chance, sending the jump to everyone, spiders holding position) is next. Leaving this open until it's in.

Closing this one: the server-side monster chase and jump work landed, so Wolf Spiders no longer follow you and then freeze in place once aggroed. Thanks for the report! If you still see a spider parked after you hit it, reopen with the map name.