I stay focused on the ramp and one of our ranged dps is assigned to call out that he's moving and which way he is heading. If the call is prompt, you can get back up in 0-2 ticks. However, three is not unheard of even on a fairly quick run back up, especially if the tank covering the spot had to move from one of the northern platforms. We require everyone to have the hp to survive three buffets before coming on the fight...that stamina gear helps on astromancer as well.
If you're constantly getting him in 1-2 buffets you're doing fine. If you're struggling a bit, swiftness potions can make a nice difference. We used them for learning and I still carry a stack for emergencies.