What they're doing is mix & matching their gear builds.

Make sure u have these 3 loadouts.

All int gears (zaar/krak sets/amu/ring etc) = max damage & low speed

Int gears + ss (ring/amu) = decent speed & damage

Ms gears + ss (ring/amu) = max speed & low damage

Once you proc kraken u can switch to one of these gear loadouts depends on the situation.

Falling behind others? Switch to (ms + ss) to catch up to them.

Want to kill mobs on the run?
Proc krak then switch to (int + ms) & spam auto/skills

Want to kill boss? Proc krak then switch to (all int gears) For maximum damage.