Best place to use Bezerker's Insight?

So this weekend I've been mercilessly farming holiday drops at the Raptor cave, and unsurprisingly I've picked up a lot of Scrolls of Bezerker's Insight (among others, but I know where to use them). So I was just wondering where people reckon is good place to use them on a survivor, given the rather stringent 30 sec between kills requirement. Thanks for any help

If you're well-trained in the boxing dungeon, it's the best place to use

Boxing knock-out maybe?

Agreed with boxing dungeon.

I dunno, I do the boxing in HM regularly, and there are often times where I wont kill something for 30 secs, which would be a waste of the scroll

The valley in Witman's Folly has 50-60 Grawl in close to each other. Go from Port Sledge, do the valley, then rinse & repeat. You can't do the whole of Witman's with one scroll though, because there is too long between the central and east sections. Be careful not to aggro too many at once though.