I honestly do not think this is that much of an issue...

In Titan HM/EX as soon as a weight is under you, you have to move. If you do not move within 1 second or so you will get hit. I can do Titan HM or EX without getting hit by a single ground attack for the whole fight, I have like a 99% dodge rate with the 1% I get hit due to my ISP internet cutting out or my own distractions.

Yes, it is a bit deceiving that you can appear out of the damage area and still get hit but, why do people insist on going by that? Just move out of the effect immediately and you will not get hit. It seems simple enough, just do not wait to move no matter what the cast bar says.

I guess they could just make the weight of the land explode a bit sooner but people will slow reaction will still get hit so same result.