Well the first wave of troops storm Echo Base shortly before the shield is destroyed.
And imminently after the shield is destroyed it appears as if Vader is already in Echo Base and Blasting through in to the command center.
That is why I thought about it a bit differently in terms of how the attack on Echo Base was staged because Vader's objective was to capture and not Nuke Echo Base from orbit or stage a risky air battle against a well equipped x-wing fighter squadron.
It would be far easier to sprint fourth on the terrain that was cleared by the AT-AT's against a decimated ground force that were fleeing for their lives whilst the shield was still up and the rebels were concentrating on escape and also escaping in to an unprotected hostile zone in outer space surrounded by Star Destroyers and Tie Fighters.
The problem is with tie fighters on Hoth atmosphere is it kind of contradicts the scene of Luke taking off and the whole vibe that all is ok and there is no longer anything to fear as they are leaving without confrontation. Otherwise I would be all for it. But It also makes more sense for the ties to be further away to intercept in outer orbit the rebel ships that are trying to escape