The SURVIVAL dlc have zero GS requirement to play and the REST OF THE GAME remain unchanged. Why we need Tier5 and GS256??

The current World Tier mechanic makes the people with proper GS256 in Tier5 have the exact same amount of difficulty during missions as in Tier4 with proper GS229. DZ experience remain unchanged. Would it be simpler to open Heroic mode in Tier4 for those min-maxed player to have a real challenge (e.g AI combat in the Hunter)??

Would it better to allow us to keep the current 229 setup with minor adjustment of the new named gears and armor damage so every player will not spent time to grind the more or less the same gear pieces again?

Would it be more fun that 1.6 LAST STAND will have more story line that are Challenge and Heroic only available in Tier5 that players NEED the GS256 to complete with??

For me right now the Tier5 and GS256 has no reason to be exist other than wasting players time again. What I'm propose is that new GS should have a solid reason for that. What we need is a meaningful progression that worth our time to play with. What do you think?