>>19766886
The impacts hits are pretty weak in the first place, and if you do go for them you limit your movement since you have to pick you want to use the jetpacks to assault or to move with. And you want to use them for movement most of the time to make sure you get as close as possible to the enemy due to random charge range (worst thing ever is to lose a model to overwatch and fail a charge).
Combined with the fact that you don't get to strike at initiative 5 anymore, you end up losing significantly more models in assaults.
6 edition is kind of a big fuck you to BA, fast is ruined, no DoA, assault and FC nerfs, but hey, you can spam fliers after you buy the new models! FUCK YEAH, GW!
Honestly, if you want to an assault army that won't fold like paper and actually can win assaults you may want to consider Grey Knights, or wait for the Chaos Dex to see how World Eaters shape up.