If some hashing power remains to solve blocks at this diff...

I'm actually wondering if this is a genuine multipool or an attack on smaller altcoins. It makes no sense for the multipool to go any further than diff 20-25 before buggering off because it's wildly unprofitable beyond that point. To push it all the way to 121 they're losing more potential earnings than they are making. This is what I meant with the diff swings becoming dangerously large, with every hit the diff was pushed higher (and fell lower) it's the same way you sink a ship by running a group of people left to right.