If you are hit with frost armor, you are still going to not be able to catch them, even with minor speed. The shaman part makes sense, but still involves them shifting out of GW to keep you in combat. The only time you would need to catch another warrior is if they are running away from you, and if they are trying to run away they should have hamstring on them. If they somehow don't, and you do, you can still easily catch them. If they turn around to hit you with ranged to keep you in combat, they stopped their movement and will get you close enough to get another hamstring. If they are turning around every 5 seconds to hit you with ranged, and they have minor speed, they are eventually going to stop just out of thrown range, giving you time to get out of combat, run into charge range, and reapply.