Skirmishes scale the way fates do, so the more people who participated in the last one, the stronger the next one that is connected to it will be.

If it's not connected it may not take into account who fought the others (such as the skirmishes that spawn CEs).

That's why if everyone enters a CE, the current skirmish can be very hard to kill, and when they finish the CE the current skirmish which is scaled to 1 person gets destroyed in seconds.