If from the start of the dungeon the tank is speeding off, then you probably don't have time to stop and type. Swiftcast Eos and follow them as soon as they start moving.
As SCH pre-Stormblood I was already timing my Adlo for the next pull to be applied just as the last mob from previous trash is dying. That way there is no downtime.
Regardless, there are ways to adjust to a sprint-happy tank. I was surprised when I had one for my first ever level 70 dungeon (as WHM). Panicked a bit, if I'm honest, but managed to keep up just fine.
