I just dont get people saying that you "can't" level up to 70 with the i270 peotic equipement or that you couldn't do it in HW with the i130 one...

It is perfectly fine to do so. I remember in HW having level up WAR to 60 with the full i130 poetic set and didnt have any trouble.

And you can do the same in stormblood. The stats difference between the i270 set and the stuff from dungeon isnt as huge as people make it out to be.

Granted this time you do get an automatic drop at the end of leveling dungeon but its not the end of the world if you dont farm dungeon for better loot or buy HQ stuff. Now if you had worse gear that the 270 poetic set to begin with thats another story...